Physical Observations of Very Young Dynamical Families of Asteroids
A Proposal submitted to the NSF "Planetary Astronomy" Program
14 November 2003
Principal Investigator:
Clark R. Chapman (cchapman@boulder.swri.edu)
Southwest Research Institute (SwRI)
Suite 400, 1050 Walnut St.
Boulder, CO 80302
Co-Investigators:
William J. Merline (SwRI)
David Nesvorný (SwRI)
Eliot F. Young (SwRI)
Peter Tamblyn (Binary Astronomy)
Collaborators:
Petr Pravec (Astron. Inst., Ondrejov, Czech R.)
I. INTRODUCTION
Synopsis
An extraordinary discovery by Co-I Nesvorny (Nesvorny et al. 2002, 2003) presents a stunning opportunity to
address, for the first time, some fundamental issues in planetary science, including the rates of processes that
physically affect asteroids. Here, we propose a carefully coordinated program of astronomical observations of
members of three special families of asteroids. Perhaps the most vital but difficult-to-obtain kind of planetary fact is
the absolute age of an event. Until now, the only precise dates for such events were from radioisotopic dating
techniques (e.g. of moon rocks, meteorites, terrestrial rocks). However, many such ages are compromised since we
don't know where the rocks come from -- which unit on Mars, which asteroid, etc. Therefore, most insight about
absolute chronologies of planetary bodies are from indirect techniques, like crater-counting, which provide very crude
ages (e.g. plus-or-minus factor of 2) for the age of, say, Ganymede's surface or the timing of an asteroid familyproducing collision. With no good absolute ages available, rates of basic planetary processes thus remain imprecise.
The brilliant discovery of Nesvorny et al., which we propose to exploit, is a robust, dynamical dating of the
formation of two asteroid families to a precision of only a few hundred thousand years! They find that the Karin
cluster (part of the famous Koronis family) formed in a catastrophic collision just 5.8 ±0.2 My ago. Also, a part of the
Veritas family formed in such a collision 8.3 ±0.5 Myr ago. And a third cluster, Iannini, is younger than either of
them. Not only are these ages unexpectedly recent (just ~0.2% of the age of the solar system) but they are known with
unprecedented precision. This is the first time that robust, precise, absolute chronological ages can be unquestionably
assigned to particular asteroids -- in this case, to members of three asteroid families. The extraordinary opportunity
that we propose to exploit is to use these youthful age-determinations to study the rates of fundamental asteroidal
processes through a suite of astronomical observations of these exceptionally young asteroid families. For processes
that have rates much longer than millions-of-years (e.g. orbital evolution of asteroid satellites, evolution of asteroid
spins), we have, at last, the opportunity to study initial conditions. For processes that have rates the order of a few
million years or less (e.g. space weathering, loss or covering of volatiles), we have a chance to study the early rates of
processes that have gone to completion for most asteroids.
We have assembled a research team with extensive experience in observational astronomy of small bodies
including (a) noted asteroid authority Clark Chapman (with decades of experience in asteroid spectrophotometry and
photometric geodesy, as well as a specialist on space weathering and asteroid families); (b) asteroid satellite expert
Bill Merline (who has discovered many asteroid satellites using adaptive optics [AO] systems on the CFHT, Keck,
VLT, Gemini, and HST telescopes); (c) small-body spectroscopist Eliot Young (a frequent observer at IRTF and with
NIRSPEC on Keck); (d) noted lightcurve specialist Petr Pravec (our overseas Collaborator); (e) Peter Tamblyn (a
specialist in computational astronomy and an IR spectroscopist), and (f) dynamicist David Nesvorný (who made the
remarkable theoretical/numerical discoveries that underpin our proposed observing program). For many representative
members of the Karin and Veritas clusters (and of an even younger group, the Iannini cluster), we propose coordinated
observations of IR spectrophotometry and radiometry (using SpeX and MIRSI at IRTF), medium-resolution
spectroscopy (using NIRSPEC at Keck), adaptive optics imaging (using VLT and Gemini), and lightcurve photometry
(using various telescopes in Europe and the American Southwest). Our goal is to search for both predicted and
serendipitous indications of youthfulness of these asteroids by obtaining observations that enable us to contrast them
with similar data previously published for normal, older main belt asteroids.
Background
The fundamental process affecting asteroids in recent aeons is mutual catastrophic collisions. They (a) create
asteroid families (clusters of asteroids with similar orbital elements); (b) produce the fragmental size distribution; (c)
rearrange large "rubble pile" assemblages; (d) provide the delta-v's that move fragments into chaotic zones, which can
radically change their orbits and remove them from the asteroid belt, sometimes into Earth-approaching paths; and (e)
establish the distribution of spins, shapes, and configurations (e.g. presence of satellites). Collisional processes also
shock, de-gas, or even melt the constituent minerals in asteroidal rocks (meteorites).
For several decades, observations of families have critically constrained asteroid collisional/dynamical evolution
(cf. Arnold 1969; Gradie, Chapman & Williams 1979; Chapman et al. 1989; and chapters in Sect. 5.1 in Asteroids III
[Bottke et al., 2002]). Based on incomplete analysis, some attributes of families seemed understood, as of a few years
ago: (a) Families are not numerous; only a few dozen have been reliably established. (b) Most families are inferred to
be very old, with ages of hundreds of millions to billions of years. (c) Families generally represent the break-up of
homogeneous precursor bodies; that is, the spectral properties (taxonomic types) of family members are usually similar
and often distinct from background asteroids in the same region of the belt. We have found preliminary evidence (e.g.
in the Sloan Survey [Ivezic et al. 2002]) suggesting that Karin cluster members, like Koronis members generally, are
S-types while Veritas members are varieties of C-type (indications of greater heterogeneity among Veritas members
{DiMartino et al., 1997} may be in error, in our opinion, based on disparities with data from Bus, 1999). Family
attributes (a) & (b) appear compatible with a developing appreciation from hydrocode modelling of asteroid collisions
(cf. Benz & Asphaug 1999) that it is difficult to catastrophically fragment, disrupt, and disperse large asteroids, so
relatively few families have formed in recent aeons.
This picture has recently been augmented by detailed dynamical analysis and numerical simulations. It is now
realized that families are subject to slow spreading and ultimate dispersal due to often-minor resonances in the belt.
Moreover, smaller asteroids are moved, over longer durations, by the Yarkovsky Effect (due to asymmetric absorption
and re-radiation of sunlight), further dispersing families. Therefore, instead of family dimensions and shapes directly
reflecting the immediate outcomes of cratering events or catastrophic disruptions, they reflect this dynamical diffusion,
often etched by chaotic zones at the borders of, or even within, the families. Therefore, it is vital to find a young, justformed family in order to compare with predicted outcomes of hydrocode simulations of collisions.
Now, one of us (Nesvorný) has led research yielding an unexpected, startling, but robust result (Nesvorný et al.
2002): a portion of the Koronis family -- one of the large families identified by Hirayama nearly a century ago -- is
apparently the product of a disrupted moderate-sized (~25 km diameter) Koronis family member only 5.8 ±0.2 My ago
(< 0.2% the age of the solar system, "yesterday" in relative cosmic terms). (Fig. 1 shows a simulation of such a breakup.) The largest member of this cluster of 75 asteroids (up from 39 known a year ago) is 832 Karin, so we call it the
Karin cluster. It is not wholly unexpected that at least one family might be as young as only 5.8 My because the
expected frequency of disruption of 25 km asteroids (the rough diameter of the Karin cluster precursor) suggests that
the most recent disruption would have occurred ~10 My ago. Remarkably, we have not only identified the family but
have precisely dated the event! So we now know we have a nearly pristine family, a "snapshot" in the immediate postcollision phase, before dynamical diffusion has progressed far at all.
Now we can undertake all kinds of potential tests for time-dependent asteroidal phenomena and behavior, which
should have evolved little since the family formed. We propose a suite of observations to determine specific
characteristics (e.g. lightcurve periods, presence of volatiles, radiometric fluxes) of Karin cluster members.
Unexpected attributes of very young asteroids might also be revealed. Among the phenomena with observable
attributes or consequences that evolve or mature over time scales of tens of thousands of years to billions of years, but
which might be incomplete after just a few million years, are: space weathering of asteroid surfaces, tidal evolution
and collisional destruction of asteroidal satellites, sublimation of large ice pockets that may have survived within the
parent asteroid but are now at or near the surface of disrupted fragments, and Yarkovsky dispersal of family members.
We can also study traits of members of a truly freshly-formed family (e.g. shapes, spins, bias-corrected size
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distribution) to compare with predicted outcomes of hydrocode simulations of collisional disruption and family
formation.
Very recently, Nesvorný et al. (2003a) have found that another family (Veritas) is also extremely young, 8.3 ±0.5
My. In the same paper, Nesvorný et al. offer a powerful dynamical argument that yet another small cluster, associated
with 4652 Iannini, is even younger than Karin, <5 My, although in this case a precise age determination is not
possible. Thus, in addition to proposing a suite of focused telescopic observations of a sample of Karin cluster
members, we propose similar observations of many members of the Veritas family (which, being composed of C-types,
is complementary to the apparently S-type Karin cluster), and of the Iannini cluster (which has 27 members, if we
include the bright object Nele, of which 19 will be brighter than V=18 sometime during July 2004 – Dec. 2007).
Since Iannini is an even younger cluster -- though its precise age isn't known -- it presents the very youngest asteroids
known! Our proposed observations will provide diagnostic tests of issues of young-vs-old asteroid families,
employing infrared spectrophotometry (at both low- and moderate-resolution), radiometry, adaptive optics imaging,
and extensive lightcurve photometry. The broad array of techniques that we intend to employ may also lead to
serendipitous discoveries of unexpected attributes of exceptionally youthful asteroids. We propose to observe many of
the currently identified Karin cluster members, a large statistical sample of Veritas members, and as many of the few
Iannini cluster members as possible -- perhaps ~100 asteroids in all (obviously fewer for techniques restricted to
brighter objects, like AO imaging). We will usually observe brighter members to reduce integration times, but will
spend some time sampling a few faint (V~19.5) family members at adequate S/N, to study potential size-dependencies.
II. TECHNICAL BACKGROUND
During the 1990s, new methods of reliably identifying asteroid families revealed a few tens of families (Zappalà et
al. 1994). Researchers look for clusters of asteroid positions in the 3-dimensional space of the so-called proper orbital
elements (which average over the rapidly varying osculating elements): proper semimajor axis aP, eccentricity eP, and
inclination iP. Proper elements are much more constant over time than instantaneous orbital elements; thus a cluster in
proper-element space suggests common ancestry. In recent years, improvements in proper element calculation and
clustering algorithms have finally yielded reliable family identifications (Milani and Kne_evi_ 1994); see Fig. 2. As
asteroid discoveries rapidly increase, family identifications have also multiplied. Recently it has been learned that
members of families gradually drift apart in (aP,eP,iP) space (Bottke et al. 2001, Nesvorný et al. 2002b). So the
youngest families are expected to be those that are still compact.
Co-I Nesvorný et al. (2002, hereafter NBDL02) applied the Hierarchical Clustering Method (HCM, Zappalà et al.
1994) to a new, state-of-the-art proper element database (Kne_evi_ et al. 2002, http://hamilton.dm.unipi.it/
cgi-bin/astdys/astibo) to search for compact families with just 1/10th of the typical separations of most families. They
found a prominent, compact cluster of 39 asteroids (including Karin) within the Koronis family (see Fig. 3); its orbital
distribution is diagonal in (aP,eP) and fits inside the similarly-shaped "equivelocity" ellipse shown in Fig. 3 (cf.,
Morbidelli et al. 1995). Simulations match the ellipse if the precursor body was near its perihelion when a
catastrophic collision and break-up occurred, launching fragments away at ~15 m s-1. Cluster fragments then circled
the sun as a group. But within ~1000 years, they drifted away from each other around their nearly common orbits.
Over longer durations, their orbital orientations (longitude of ascending node, argument of perihelion) also drifted
apart, around 360º, due to planetary perturbations. (It is the failure of the latter elements to fully spread in the case of
the Iannini cluster that demonstrates its extreme youth.) After only a few million years, the once-clustered asteroids
had dispersed into a toroid around the Sun, like the IRAS dust bands (only aP,eP,iP, remain tightly clustered for long
durations). By numerically integrating the orbits back in time to an instant when all the orbital elements are clustered
(Fig. 4), NBDL02 could find the absolute time when the Karin cluster formed: ~5.8 My ago. (The chance that such a
convergence could happen by chance during the full age of the solar system is <10 -6!) This first-ever dated event must
not be confused with the event that created the Koronis family. The age of the Koronis family, based on cratering
studies of Ida (a Koronis member) and collisional/dynamical evolution studies, is 2-3 Gy (Chapman 2002, Marzari et
al. 1995, Bottke et al. 2001), more than 400 times older than the Karin-cluster event, which is a very recent secondary
disruption of an asteroid within the Koronis family. (Indeed most asteroid families have indirectly-inferred, lowreliability ages that are very old [cf. Marzari et al. 1995], often billions of years.)
A similar search by Co-I Nesvorný et al. (2003) yielded another tight cluster around the outer-belt asteroid 1086
Nata, within the classical, unusually compact Veritas family (cut off from the rest by a chaotic resonance). Because of
the compactness (Fig. 2), Milani & Farinella (1994) previously suggested that the Veritas family is <50 My old.
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Nesvorný et al. (2003) analyzed the evolution of nodal longitudes of relevant Veritas family members (like the upper
panel of Fig. 4) over 50 My, yielding (Fig. 5) a prominent convergence of many orbits ~8.3 My ago. This is
surprisingly recent, given that disruptions of asteroids as large as ~140 km diameter (the scale of the Veritas precursor
body, Tanga et al. 1999) occur rarely. Probably the Veritas family is really older, but a smaller family member
disrupted only ~8.3 My ago, which produced Nata and those Veritas members that contribute to the conjunction shown
in Fig. 5. (The chance of this conjunction occurring accidentally over the solar system's age is <10 -5.) Nesvorný et al.
(2003) also describe why the small Iannini cluster must be <5 My old, even though a specific date for disruption
cannot be calculated.
III. GOALS AND OBJECTIVES
Because we have determined the absolute ages of two very recent asteroid collisions, we have the first and
far-reaching opportunity to study time-dependent phenomena that affect asteroids by contrasting observations of these
clustered asteroids with more ancient asteroids. We have designed our three-year observing program to test several
predictions or expectations concerning very young asteroids, in addition to looking for serendipitous attributes of these
bodies. Beyond our primary objectives (described below), our data will also augment the general data sets on asteroid
physical properties.
Space weathering
Preliminary data, obtained by R. Binzel at our request, suggest that Karin cluster members are S-like asteroids, like
other Koronis family members; Sloan Survey data of 3 others are also S-like. Indeed one Koronis member, 243 Ida,
has been a prime test case for the existence of "space weathering" on S-type asteroids (Chapman 1996, Chapman
2004). Space weathering is the phenomenon, possibly due to micrometeorite impact and solar wind impingement, that
modifies spectral reflectances from that of the inherent mineral assemblage. Many S-types, for example, may be
ordinary chondritic (OC) in composition, but the diagnostic spectral shape and depth of absorption bands are space
weathered into a typical S-type spectrum, characterized by a reddish continuum and shallower absorption bands.
Binzel et al. (1996) observed a full range of spectra among small Near Earth Asteroids (NEAs), from OC to traditional
S-type, suggesting that there is a range of collisional ages, with recently "freshened" surfaces looking like unmodified
OC meteorites (from lab spectra) while progressively older asteroids are more maturely space weathered.
We would expect that Karin member surfaces are all the same age, 5.8 My (not to rule out some slight subsequent
modifications). Our low-res spectra will reveal the degree of space weathering (from spectral slope and the 1 and 2
μm band depths). Since published estimates of space-weathering timescales range widely from 50,000 years to 100
My (Hapke, 2001; Sasaki et al. 2001), it will be vital to understanding space weathering processes to determine the
degree to which spectral evolution has matured on the 5.8 My-old Karin family members. We can even test whether
space weathering rates are a function of body size, which might be expected if the processes that comprise space
weathering are mediated by regolith processes, which in turn depend on a body's gravity. Thus the Karin cluster, with
its precisely known age within the range of space-weathering timescales, presents a ready-made laboratory for testing
space weathering hypotheses. Such processes must affect C-type asteroids, as well, although spectral effects may be
smaller than for S-types (cf. Sect. 7.2 of Rivkin et al. 2002); so we will make similar observations of C-type Veritas
family members. Indeed, this is a perfect opportunity to understand how space-weathering differently affects C- and
S-types, calibrating the early changes before maturity is reached. Space weathering processes are believed to be
material-dependent, so we are fortunate that our two young families are so compositionally distinct (the taxonomy of
the Iannini cluster is not yet known, but we will study these exceptionally young asteroids, as well, to determine their
taxonomy). Our studies will augment the partial understanding of space weathering already achieved from spacecraft
investigations of Ida and Eros (cf. Clark et al. 2002).
Volatiles
Asteroids are generally thought of as rocky and comets as icy. But water ice probably formed within the asteroid
belt and could have been stable for aeons within asteroid interiors, despite readily subliming from asteroid surfaces.
Indeed, there were published 3 μm indications of water frost on Ceres, although that is now largely discounted. The
freshly created Karin and Veritas asteroids provide our best chance to search for remnant water ice (and other
volatiles, like methane and CO2, all with characteristic IR bands) on asteroid surfaces. For example, if the Veritas
precursor body had large chunks of ice within its deep interior 8.3 My ago, ice might have been at the surfaces of some
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fragments when the family was created. Depending on ice thickness, it might still be there to be detected, provided -for example -- that it hasn't been covered over by ejecta from a recent cratering event. One might expect ice to be
found in "dry" C-types (Rivkin 1997) in the Veritas family rather than in either Karin cluster S-types, which have been
heated at least to metamorphic temperatures or in "wet" C-types, which are inferred to have been thermally processed.
Such theoretical expectations deserve to be observationally tested, so we will look at examples of each type. (Most,
but not all, of Veritas members are of the "wet" variety [Bus & Binzel 2002].) Other ices and organic compounds
might also last for millions of years while generally vanishing on the longer time scales that apply to typical asteroids.
Since we can imagine that remnant ice pockets might be much smaller in size than the family members themselves, we
propose to obtain spectra at higher S/N for these compositional studies as well as at the somewhat higher spectral
resolutions that will reveal and distinguish volatile signatures -- accordingly, NIRSPEC on the Keck is our choice of
instrument for this purpose. The rather broad IR spectral bands of ices, hydrated silicates, and organics can be
intermingled (e.g. near 3 μm), but much literature (e.g. as reviewed by Roush & Cruikshank 1994) is devoted to
resolving volatile compositions in the outer solar system, and is applicable to interpreting our own data, which will be
obtained with similar observing techniques.
Satellite Formation and Evolution
Only a decade ago, asteroid satellites were a theoretical curiosity. With the discovery of Dactyl during the Galileo
flyby in 1993 (Chapman et al. 1995; Belton et al. 1995) and the first verifiable detection from Earth of a satellite
orbiting a main-belt asteroid (Merline et al. 1999), using adaptive optics (AO), we have begun a revolution in asteroid
science. Satellites of asteroids are important (1) as natural laboratories in which to study the cratering and catastrophic
collisions that form and destroy them; (2) because their presence permits determination of the primary asteroid's bulk
density, which is otherwise generally measurable only by spacecraft missions; and (3) the evolution of satellite systems
(e.g. influenced by tidal forces) is related to spins, configurations, and interior structures of the bodies involved.
Binaries have now been detected in various dynamical populations, including Near-Earth, main belt, outer main belt,
Trojan, and trans-Neptunian objects (TNO). Detection of these new systems has resulted from improved observational
techniques, including AO on large telescopes (applications to asteroids have been pioneered by Co-I Merline), radar,
direct imaging, advanced lightcurve analysis (mostly by Collaborator Pravec), and imaging by interplanetary
spacecraft (again led mainly by Co-I Merline and PI Chapman). Systematics and differences among the observed
asteroid satellite systems are revealing vital clues to the formation mechanisms.
A young family, like Karin or Veritas, presents an exceptional opportunity to study the formation of asteroid
satellites. Among the three leading mechanisms for forming main-belt binary asteroids, one involves just the type of
catastrophic disruption that created the Karin and Veritas families (Merline et al. 2002b). Early models of Durda
(1996) and Doressoundiram et al. (1997), as well as more sophisticated models being done by Durda et al. (see Fig. 1)
indicate that these systems (small primaries, with a widely-separated secondary) are commonly formed in catastrophic
collisions. Once formed, smaller satellites are subject to collisional destruction on timescales of millions to tens of
millions of years. Therefore, members of recently formed families would be especially likely, in this model, to retain
observable satellites; our understanding of asteroid collisional lifetimes could be tested by searching for satellites
among the members of these young families, which have ages similar to the collision lifetimes of satellites. Young
asteroid satellite systems also have had little time for significant tidal evolution of orbits or spins -- the system will be
nearly "pristine", revealing the initial spins and orbital configurations of first-generation satellites immediately
following a catastrophic disruption. (Ida's Dactyl, in contrast, is believed to be an nth generation satellite, having been
disrupted and reaccreted several times.) Timescales for tidal evolution of the objects we consider here are quite long,
some tens to hundreds of millions of years (Weidenschilling et al. 1989). Indeed, these are ideal systems to search for
triple or multiple systems! Expected characteristics of multiple systems are discussed by Merline et al. (2002b).
Current numerical models of satellite formation by catastrophic disruption by Durda et al. (Icarus, in press, 2004)
indicate that soon after disruption many objects may have multiple components. Our proposed observations could
enable us to study the lifetimes of such multiple systems, elucidating and calibrating the dynamical stability of such
systems and the collisional mechanism that produces them.
In Feb. 2002, Merline et al. (2002a; 2002c) discovered what is probably the first example of a binary system
created by this mechanism of disruptive capture (see Fig. 6). Among main-belt binaries, this system, 3749 Balam (a
member of the Flora family), at first stood out as an oddity: a very loosely-bound system, even more so than most TNO
binaries. The secondary orbits at least 100 (primary) radii from the primary, which itself is just ~7 km diameter.
Because such systems are faint, only a few have been searched for satellites before now. Because we expect the
separations to be large (binaries formed by the two other mechanisms must have small separations), we can then make
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powerful statements about the prevalence of satellites formed in catastrophic collisions; in turn, this can guide the
now-rapidly-developing field of numerical simulations of satellite and family formation. In Feb. 2003, Merline et al.
(2003) discovered another such widely separated system, 1509 Esclangona, probably also the result of a disruptive
capture.
We have been awarded a large HST program (Merline PI; Chapman, Tamblyn, & Nesvorny Co-Is) to search
for satellites of small Karin and Veritas members. We specifically chose limits that would complement this proposed
ground-based search. The limits to ground-based AO are V=17.5, so our HST limits are V=17.5-19.5. We propose
here to survey those objects brighter than V=17.5 so that our study may span a larger size range (clearly, HST would
not support observations of brighter objects that could be made from Earth). The faint limit (V=19.5) of our HST
program was chosen to provide satellite data on the fainter objects for which we will obtain lightcurves, thermal, and
spectral data in this proposed groundbased program. We obtained the first positive results from this HST program in
the first download of data in July 2003, in which we discovered a companion to asteroid 22899 (1999 TO14) (Merline
et al., 2003b). Although this object is not a Karin or Veritas member, it is a Koronis family member that we are using
as a control. The primary is only 4.5 km diameter (making it the smallest main-belt binary known), and the companion
is only 1.5 km diameter (the size of Dactyl). Clearly, this wide binary is another example of the systems we seek to
observe here.
Calibrating the Yarkovsky Effect
The semimajor axis mobility caused by the Yarkovsky effect (Öpik 1951) has assumed major importance in
understanding the long-term dynamical evolution of asteroids, including delivery of meteorites and NEAs to nearEarth space (e.g., Farinella & Vokrouhlický 1999, Bottke et al. 2002, Morbidelli & Gladman 1998, Morbidelli &
Vokrouhlicky 2003). Current models of the Yarkovsky effect, however, rely on poorly known parameters that
characterize the composition and spin state of asteroids. Accordingly, Co-I Nesvorny has developed a novel method
that uses the Karin cluster to precisely measure, for the first time, the semimajor axis mobility that asteroids experience
in the main belt (based on evolution to current positions from a known time and location of formation).
To compare these drift rates with theoretical models of the Yarkovsky effect, we wish to know as much as possible
about (1) size, (2) density, (3) albedo, (4) rotation rate, (5) obliquity, and (6) surface conductivity of Karin cluster
members. Here we propose to determine attributes 1, 3, and 4 for representative members; if satellites exist, we can
determine density and our lightcurve observations will start to constrain obliquity for some objects. We may then
calculate what values of surface conductivity are compatible with the determined drift rates, thus constraining the
surface properties. In a broader sense, this work will allow us to check, for the first time, theoretical models of the
Yarkovsky effect. Our work on this task will complement very recent radar efforts that successfully detected the
Yarkovsky effect on a natural body, 6489 (Chesley et al. 2000, 2003). Rather than NEAs, our studies concern a large
sample of multi-km asteroids, with various sizes, obliquities, and spins in their main-belt environment.
Checking Hydrocode Simulations of Asteroid Disruption
We and our colleagues are undertaking SPH simulations of the catastrophic break-up of asteroids, including the
Karin cluster parent body (see Fig. 1). Obtaining good data on the physical attributes of the immediately post-breakup Karin cluster (and other young clusters) will help us better understand the physics of large-scale collisions, the
mechanism that helped shape the planets at early epochs (Chambers & Wetherill 1998, Canup & Asphaug 2001). To
correctly set up numerical experiments and check results against ground truth, we need to observe and determine the
sizes, densities, and spin properties of Karin cluster members.
Broader Social Context and Public Outreach
Our research objectives concern the processes that created asteroids and cause their continuing evolution,
including delivery of some of them (and their fragments) from the asteroid belt to Earth. Asteroids, as well as the Sun,
are the two parts of the extraterrestrial universe that have direct manifestations on Earth. In the case of asteroids, the
direct relevance is the continual rain of bolides and meteorites onto our planet, as well as the (very low-probability)
threat of devastating impacts by 100-m to km scale asteroids, like those that have helped shape the biological evolution
of our planet. Thus it is not surprising, for instance, that past NASA Administrator Goldin reportedly said that
"asteroids" ranked second in the number of letters he received from the public. Thus we asteroid researchers have
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fortunately been on the frontlines of interfacing with children and adults alike, whose curiosity about asteroids and the
potential hazards they present are often their first introduction to astronomy or even science.
The P.I., Dr. Chapman, has had a lifelong commitment to education and public outreach, which was
recognized by his being awarded (1999) the AAS DPS Carl Sagan Medal for "Excellence in Public Communication in
Planetary Sciences." His activities, almost wholly unfunded, have included writing popular books and articles,
appearing in TV documentaries (like Nova), curating a museum science exhibit, giving classroom and public lectures,
participating in moderated web-chats (e.g. concerning Astrobiology), responding to journalist inquiries, and so on. He
currently serves as Liaison between the Science Team and the EPO effort of NASA's MESSENGER mission to
Mercury. Dr. Chapman's EPO activities within several weeks of the submission of this proposal (mid-Nov. 2003) are
representative: (a) answering dozens of inquiries from the public concerning a feature article in the Nov. Scientific
American co-authored by Chapman; (b) publication of an essay co-authored by Chapman (selected by Richard
Dawkins) in Houghton Mifflin's "The Best American Science and Nature Writing--2003"; (c) co-author of a
MESSENGER EPO talk at Fall AGU and invited author of an interdisciplinary plenary Union talk at AGU; (d) public
evening talk about asteroids at Little Thompson Observatory in Berthoud, Colorado; (e) invited submission of Letterto-Editor of New York Times concerning science journalism; (f) appearance on 2-hr CBC/BBC-TV documentary on
asteroids Nov. 24th; (g) participation (with astronauts Rusty Schweickart and Ed Lu) in activities concerning a
possible asteroid mission through the public B612 Foundation; and (h) coordination of EPO activities in the Boulder
Office of SwRI. Several other Co-Is of this proposal often engage in similar activities.
We are thus pleased with NSF's encouragement of such activities and have a specific goal of emphasizing the
public dissemination of our research activities in numerous different ways as our research progresses. Some of these
EPO activities will be proactively arranged by us, while others will arise serendipitously, since Dr. Chapman and other
Co-Is are frequently solicited by teachers, museum staff, etc. to participate in EPO projects. We will specifically try to
explain in ways accessible to the lay public the rather technical project that we propose herein, but we expect that most
of our EPO efforts will relate to asteroids more generally, in ways immediately relevant to public curiosity. There is,
after all, a connection between our trying to learn about asteroid collisional processes by studying the youngest breakups (before the family members have dispersed or been modified by subsequent collisions or space weathering) and
the public fascination with rocks -- and potentially bigger objects -- falling from the skies: the collisions and
subsequent evolution of fragments that we are investigating are the very processes that bring asteroid fragments from
their distant, harmless orbits beyond Mars to make their fiery impacts onto our planet.
IV. TECHNICAL APPROACH
Introduction and Scope of Observations
We have compiled lists of known members of the Karin cluster (a=2.87 AU, e=0.044, i=2.1º), the Veritas family
(a=3.17 AU, e=0.065, i=9.3º), and the Iannini cluster (a=2.64 AU, e=0.267, i=12.2º), giving the brightest V
magnitudes attained by each object during the 3½ years after our nominal 1 July 2004 start date (space limitations
preclude presenting these lists in this proposal). Roughly 74 Karin family members, 207 Veritas members, and 25
Iannini cluster members are at least briefly brighter than V=19.5. (Based on the current rate of continuing discoveries
of main-belt asteroids and calculations of family assignments, we expect these numbers to escalate to roughly 115,
395, and 48, respectively, by 2006.) Therefore, we expect that on a typical night (Mauna Kea, zenith dist. <65º) there
will be about 15, 130, and 9 known members visible brighter than V=19.5, respectively; hence scheduling
observations to achieve our statistical samples of Karin and Veritas members is not a problem. Fewer objects will be
available at Mauna Kea during the first year-or-so of our program until a planned new guider is installed that will work
fainter than V=18; also, for some of our other proposed studies, magnitude limits are brighter than 19.5, so we will
concentrate on brighter objects that are available. Fig. 7 shows V magnitudes for those Karin and Iannini family
members that are currently known (i.e. not escalated to 2006), during the 3½-year period beginning July 2004 during
which this program will be conducted, showing the number that rise brighter than various magnitude limits for the
types of observations discussed in this proposal.
Our program uses several different observational facilities and instruments, each carefully chosen and suited to a
specific task. We have previous experience proposing for and using these facilities. Our track record shows that we
can successfully compete for time at large telescope facilities. Due to the usual vagaries of telescope time
7
assignment, weather, etc., we cannot specify which particular asteroids we will succeed in observing with which
combination of observing modes, nor to exactly what level of S/N. Our approach is not to observe every member
(after all, many members remain to be discovered!), but rather to observe (a) many of the known Karin cluster
members, (b) a large, representative sample of Veritas family members, and (c) many of the Iannini objects (a small
cluster that nevertheless has some moderately bright members). We will try to cover as wide a range of sizes for each
group as possible with each technique, emphasizing brighter objects but giving some priority to the longer integrations
needed to obtain a few fainter objects.
Our approach will generally be to obtain data similar to data that have already been obtained -- often with the same
telescopes and instruments -- for other main-belt asteroids by other observers. By using similar observing modes and
data reduction procedures, our data can readily be compared with other archived data, in order to clearly detect
differences among young family members and other categories of asteroids. Our observations will be made with
spectral resolution and S/N, using facilities specified in Table 1 (keyed to goals by abbreviations), so as to address
several key determinable properties of the individual members of these dynamical families:
* SW: slope of the near-IR spectrum and absorption band parameters, which define the extent of space weathering on
these bodies, obtained at low spectral resolution.
* TAX: taxonomic type of the objects, which will help relate these bodies compositionally to those in other families
(e.g. as observed elsewhere in the main belt by Bus, 1999). (Note: although taxonomy was traditionally defined in the
visible and near-IR, later studies demonstrate the correspondence of types as measured in the 0.8-2.5 μm range.)
* SPIN,SHAPE: object spin periods and lightcurve amplitudes, which can be analyzed in the context of similar data
for other asteroids, relevant to body shapes and dynamical evolution. In some cases, we can obtain lightcurves from
several geometries, permitting us to determine or constrain obliquities (P.I. Chapman is familiar with this approach as
a participant in the PSI Photometric Geodesy program, cf. Weidenschilling et al. 1987).
* SIZE,ALB: thermal flux measurements, which, together with the visible lightcurves (taken simultaneously, or
nearby in time, such that we know the lightcurve phase during the radiometric observations), will yield albedos and
sizes of the objects, using the Standard Thermal Model and more sophisticated techniques (cf. Lebofsky & Spencer
1989).
* SAT: existence of (or limits on sizes of) satellites of the objects.
* VOL: medium resolution spectra of a selection of the objects to search for (or set limits on) the presence of ices or
other volatiles, which may have survived since break-up on or near the surfaces of some young objects.
Our baseline schedule of observing runs is outlined in Table I.
Table I. Summary of Planned Observing Runs
Year Run#
Where
#
#
Instrument
Nights Persons
Measurement
Science
Goals
1
1
1
1
1
2
3
4
Keck
VLT
IRTF
Arizona
2
2
5
7
2
2
2
2
NIRSPEC
NACO
SpeX/MIRSI
CCD photom
MRES
AO
LR;TH
LC
VOL
SAT
SW,TAX;SIZE,ALB
SPIN,SHAPE
2
2
2
2
2
5
6
7
8
9
IRTF
Keck
VLT
IRTF
Arizona
5
2
2
5
7
1
2
1
1
1
SpeX/MIRSI
NIRSPEC
NACO
SpeX/MIRSI
CCD photom
LR;TH
MRES
AO
LR;TH
LC
SW,TAX;SIZE,ALB
VOL
SAT
SW,TAX;SIZE,ALB
SPIN,SHAPE
3
3
3
10
11
12
Gemini
Arizona
IRTF
2
7
5
1
1
1
Altair/LGS
CCD photom
SpeX/MIRSI
AO
LC
LR;TH
SAT
SPIN,SHAPE
SW,TAX;SIZE,ALB
8
3
13
IRTF
5
1
SpeX/MIRSI
LR;TH
SW,TAX;SIZE,ALB
In addition to the specific runs tabulated here, there will be numerous opportunities to acquire
lightcurve data through the local Univ. of Colorado facility and via our Czech Collaborator P.
Pravec, during some of his regularly-scheduled observing nights. Efforts will be made to
coordinate observations of this program with other runs we may fortuitously have on any of these
same telescopes.
Key:
LR = low-resolution spectra 0.8-2.5 μm; R~25
TH = thermal IR radiometry, N band (10.6 μm); 20 μm, weather permitting
AO = high-spatial-resolution near-IR imaging by adaptive optics (resolution ~0.05 arcsec,
or ~70 km at the range of the Veritas family)
LC = time-resolved visible photometry to determine the lightcurve
MRES = medium-resolution spectroscopy (R~100) over the range 2.2-4.2 μm
"VLT" is the ESO Very Large Telescope Facility, located on Cerro Paranal, in Chile. It is a
complex of four 8.2-m telescopes; one telescope is dedicated full time to the NACO AO facility.
NACO combines their new Shack-Hartmann AO system, with CONICA as the science imaging detector (InSb
detector, 1024x1024, 1-2.5 μm). We already have European collaborators for the VLT AO program of
Merline et al. (and demonstrated performance down to V = 17.4). But Co-I Nesvorný and Collaborator
Pravec, both Europeans, will qualify our proposals as "European", and thus they cannot be downrated
because of lack of European participation.
"Arizona" represents an as-yet unspecified site within Arizona: KPNO (NOAO), Lowell Observatory,
Vatican (with whom we've already had informal discussions), Univ. of Arizona Observatories (UAO),
Planetary Science Institute (PSI). For our lightcurve work on objects fainter than V=17.5, we
require a ~2-m class telescope, of which there are many. We expect access via our numerous
collaborations and/or through normal TAC process (such as to NOAO). Examples include Lowell 72",
Kitt Peak 84", PSI-operated Kitt Peak 50", UAO 61" & 90", and Vatican VATT 1.8-m (among us, we have
used all of these example telescopes in the past). CCDs for photometry are common astronomical
instruments and we anticipate access to a CCD at any of the above sites (we, at SwRI, also have our
own CCD camera that would be suitable).
"Altair/LGS" is a planned upgrade to Altair, expected to be ready for operation in 1-2 years.
Altair is just now being brought on-line using natural guide star (NGS), i.e. guide-on-target.
Altair in NGS mode will be able to achieve good AO-correction on objects only down to ~15.5 Vmag.
Therefore, laser-guide-system (LGS) will be required to observe many of our targets. Once LGS is
available, we should be able to achieve AO-imaging of V=17.5 targets.
We now provide more details on how each suite of observations is designed to address a particular goal with an
efficient set of measurements.
Spectrophotometry, Spectroscopy, and Radiometry
We will obtain low resolution spectra (R=~25) to address space weathering phenomena on the very young surfaces
of cluster members and to confirm or derive taxonomic type. We will use the IRTF SpeX in its lowest resolution (but
most sensitive) 0.8-2.5 μm "prism" mode. The SpeX online documentation (http://irtfweb.ifa.hawaii.edu/
Facility/spex/sensitivity.html) recommends 120-sec A-B beam switch pairs, since longer exposures would potentially
fail to remove variable OH sky emission lines; with the object in an 0.8" slit in both the A and B positions, S/N ~10 is
expected for an hour integration (15 A-B pairs) for J-mag. 18.9, H-mag. 18.4, or K-mag 17.9 (equivalent to V~20 for a
typical asteroid). The 0.8" slit produces resolutions R=60 in J, R=100 in H, and R=140 in K, but we plan to bin in
wavelength to R=25, which will yield spectral resolutions about half that of the 52-color data set of Bell et al. (1988),
sufficient to study space weathering and classify taxonomy. Such binning improves the S/N by factors of 1.6, 2.0, and
2.4 in J, H, and K filters, respectively. The S/N for a 19.5 mag. object (observable when the planned upgrade to the
tracking system is finished) is ~12 in all three filter regimes (for 1 hour, binning R=25).
There are 74 Karin cluster objects and 207 Veritas objects that achieve brightness greater than 19.5, rising to 115
and 395 by 2006. An average of 154 Karin, Iannini, and Veritas objects brighter than 19.5 magnitude will be available
at each run by 2006. (The current TCS [telescope control system] can track objects only brighter than V=18; it is
expected to be upgraded within 18 months, but even if it isn't, we still would have ~30 objects available per run, more
than we can observe.) We expect to observe 10 objects per night (at 1 hour per object, and allowing time for focus,
calibration, and standard stars), achieving S/N of 12 for the faintest objects (mag 19.5), sufficient to specify spectral
slope and assign taxonomic class, and rising up to about S/N~50 for the brighter ones. We have planned 5 observing
9
runs of ~4 nights each. If we conservatively estimate an overall time loss of 50% for weather and equipment
problems, we will conservatively obtain spectra of 20 objects in a 4-day run with S/N of 12. The expected total will be
>100 objects over the duration of the entire project. Our reduction of SpeX data will use the IRTF's SPEXTOOL
package. Its current version (3.1) fully supports low-res prism spectra. It does a nice job of dark and bias subtraction,
flat field normalization, arc lamp and sky line identification, and wavelength calibration. It also evaluates noise on a
per-pixel basis and propagates errors through the spectral extraction process. (There are some who are skeptical about
our proposed use of standard SpeX reduction techniques. But Co-I Young is thoroughly practiced in obtaining
excellent data with SpeX; he was awarded 5 nights on SpeX this past semester [2003 A], 3 as PI, 2 as Co-I. In
separate research, Co-I Young is funded to develop a pipeline for reducing data from IRTF instruments.)
From IRTF/SpeX low- res (R~25) spectrophotometry of cluster members having a range of brightnesses, we can
address how space weathering of equal-aged bodies varies with size. However, even the brightest few Karin cluster
members are difficult targets from SpeX in higher resolution modes; accordingly we will request Keck/NIRSPEC time
to observe a few Karin, Veritas, and Iannini cluster targets with higher spectral resolutions and better S/N to search for
volatiles. Spectral resolutions of R=100 or higher are preferred for this search (translating to binning factors of 22x
for NIRSPEC spectra). Even if we find no volatiles, the negative result will establish an interesting upper limit. To
make the search more sensitive, we plan to obtain a S/N of 30 (or better) per binned wavelength sample. Based on CoI Young's experience observing the Centaur Chariklo (V-mag = 17.79) with NIRSPEC at R=2,200 (see Fig. 8), the
brighter Karin and Veritas members should be straightforward spectral targets, even with our nominal S/N
requirements. We plan two Keck observing runs over the 3-year span of our project. The result will be medium-res
spectra generally over 2.2-4.2 μm of ~1 dozen objects, giving us an adequate sample to examine for presence of
volatiles. We will use the KL order-sorting filter with NIRSPEC "LoRes" mode (R=2200 binned to R=100), with total
on-target integration times ~90 min. We will restrict our observations to objects brighter than V~18. Again, there will
be plenty of targets for any run, but we will optimize our observing time requests to study the most objects.
Thermal flux measurements will be made at IRTF using the MIRSI mid-IR camera; we will make appropriate
arrangements with the P.I. of this new instrument. Radiometry at 10.8 μm (N-band) will be used to determine the
albedos of a select number of brighter family members. When conditions warrant, we will also attempt observations at
20 μm, which permits a better handle for modelling the asteroidal emissions. Observations in these two bands have
been classically used in asteroid radiometry. We expect observational limits of V~16-17 for MIRSI; we will schedule
observing requests to optimize the number of targets. We plan to use both SpeX and MIRSI during the same
observing runs; we therefore budget one additional night per run for MIRSI. As with MIRSI's predecessor MIRLIN,
we expect that MIRSI and SpeX can be routinely swapped within an observing run (indeed within a single night); thus
we can make best use of atmospheric conditions (determined by 225 GHz opacity) to select the best times to use
MIRSI within a 5-night run. We would expect to have about 6 objects observable (including Veritas members, not
shown in Fig. 7) during a well-chosen run.
Adaptive Optics Observations
We will also perform adaptive optics (AO) observations of some family members to search for companions.
Because these objects are faint, the only currently capable system (down to V=17.5) is the NACO system on the ESO
Very-Large-Telescope (VLT) in Chile. Merline et al. have completed two VLT observing runs, discovering yet
another binary of the type we propose to study, around (1509) Eslangona (Merline et al. 2003a). That program targets
certain main-belt and Trojan asteroids, but not Karin, Veritas, or Iannini members. We expect success in acquiring
time (one run per year) during the first two years of this project. In the final year we will use the Gemini telescope
(Altair); Merline et al. have used Gemini to great effect to search for satellites of faint asteroids, but the Altair/LGS
will not be available until 2004-2005, at which time Gemini is preferred because we expect shorter exposures due to
the brighter laser guide source with the new LGS system, and thus sharper target images.
Using either NACO or Altair/LGS, we will be able to search for satellites around the brightest Karin family
members; several Iannini and many Veritas members will also be accessible. The limiting magnitude at VLT is ~17.5
Vmag, but we expect Altair/LGS to allow us to work fainter, maybe even to V ~19.5. Based on our previous
experience, we expect to observe 20 objects per good night at VLT and 40 per night at Gemini. We have thus
budgeted 3 total AO runs. At 2 AU from Earth, we will resolve objects separated by ~70km at brightness ratio ~3
mag. Thus, for a 10 km primary, we could detect a 2.5 km sized satellite at separation 70 km (~5 primary radii). The
targets of our search in the proposal will be systems formed by family formation, probably co-orbiting pairs (unlike
most known main-belt binaries, which formed by large cratering events), so we expect large separations for these
10
binaries (see Weidenschilling et al. 1989; Merline et al. 2002b); thus, our secondary size limits will be even better.
Under Merline's AO program, we have developed tools to predict appulses of faint asteroids with bright stars. For our
three clusters, we expect to have a few dozen events per run. By guiding on the bright star near the asteroid we can
temporarily achieve good AO correction on the asteroid (provided it is within the isoplanatic patch of the star, which is
~20 arcsec in the near-IR).
Lightcurve Photometry
Lightcurves of the cluster members will be acquired by 3 strategies:
* For objects brighter than about V=17.5, we will employ existing facilities at the Univ. of Colorado campus, which
will allow ~3% photometry using the 24" telescope and new SiTe CCD. SwRI scientists (some of us are Adjunct
Faculty at CU) routinely use this telescope for photometry. By observing locally, we avoid travel costs.
* Our collaborator Pravec will also acquire lightcurve data, at the same precision, on his 0.65m system in Europe. An
advantage is that we can obtain better phase coverage and quicker solutions for spin periods. Furthermore, multiple
observations help us resolve ambiguities, and in particular give good lightcurve coverage in the case of an eclipsing
binary. Pravec has regular and routine access to this telescope.
* For objects fainter than V=17.5, we will obtain lightcurves with one of several Arizona telescopes. We have
budgeted one trip per year to Arizona for a week each. We expect to obtain lightcurves on as many as a dozen objects
during a good night, using standard photometric procedures and the protocol of the PSI Photometric Geodesy (in
which P.I. Chapman participated; cf. Weidenschilling et al. 1987). Allowing for 50% loss to weather we would get
lightcurves on ~125 fainter asteroids over 3 years, enough to characterize the spin-distribution and shape
characteristics of these compact, recently formed clusters.
TABLE II. Summary of Expected Observations
Obs
Type
LR
TH
MRES
AO/VLT
AO/Gem
LC
S/N
~20
~30
~30
30
Resol.
25
100
70km
70km
-
# Nights
per run
4
1
2
2
2
7
# Objects
per night
10
6
6
20
40
12
# Objects
# of
per run (*) Runs
20
3
6
20
40
40
5
5
2
2
1
3
Total Objects
(3 years) (*)
100
15
12
40
40
~125
* = assumes 50% loss due to weather, equipment, etc.
Analysis and Interpretation
Our data will be reduced using standard (but enlightened) procedures, for each of the different techniques
employed, with which we are already intimately familiar. The assembled data (Table II) will be intercompared among
family members and with more typical asteroids. We will analyze and synthesize the data in order to obtain first-order
answers to the questions posed in our Objectives; we must frankly state, however, that the majority of time budgeted in
this proposal is for data acquisition and reduction, and we must seek additional funding elsewhere for thorough
analysis of the data. Of course, these asteroid clusters are so exceptionally young that we expect some rather obvious
results will become immediately apparent as the program proceeds. Should unexpected phenomena be revealed, our
ongoing analyses may suggest changes in our observing priorities. We will give more priority to presenting,
publishing, and archiving our data and first-order results in our second and third years, and have budgeted an
additional science conference for the final year.
Public Outreach
11
We outlined in Sect. III our deep commitment to, and experience in, Education and Public Outreach (EPO)
activities. Because of the intense public fascination with asteroids and their (literal) impacts on Earth and in the news,
as well as the prominent public roles the P.I. and some Co-Is continue to play in this topic, we expect to continue to
receive solicitations for future public outreach opportunities related directly, and more commonly indirectly, to our
proposed asteroid research (note: in our non-academic, non-profit research institute, public outreach efforts are
normally a better fit for us than formal education activities). We will continue to respond positively to such
invitations, which normally involve hundreds of unfunded hours (mainly evenings and weekends) per year. In
addition, to demonstrate our commitment to these endeavors, the P.I. has budgeted 20% of his participation in this
proposed research to lead and conduct public outreach activities, related to asteroids, during this three-year program.
These will include writing at least one article per year (for public print- or web-magazines) and arranging to give at
least one public presentation per year (e.g. to schools, museums, planetariums, service organizations) on asteroidal
topics at least indirectly related to our research.
Many EPO activities emphasize two factors: (a) effective leveraging of the scarce, valuable time of often busy
and inarticulate scientists, usually accomplished through intermediaries such as professional educators, and (b) formal
evaluation of effectiveness in meeting, for example, goals of national science education standards. In our case, Drs.
Chapman, Merline, Young, and Nesvorny are all articulate, experienced speakers and writers for the lay public, and we
are sought after by entities that can bring our direct message to dozens or up to millions (in the case of TV and radio)
of children and adults; for that reason, we believe our limited time is most effectively used in being directly engaged in
public outreach activities rather than in attempting to coordinate with EPO professionals. It will be less easy for us, in
these often informal settings and involving media (like TV) beyond our control, to formally assess the effectiveness of
our public outreach activities. But we will be diligent and cognizant of the need to be effective in our communication;
we will engage in activities that reach many people and have good chances of continuing to spread beyond our
immediate readers and listeners to others of diverse ages, ethnicities, and interests. In conclusion, we emphasize our
past record (highlighted in Sect. III) of nationally-recognized EPO activities as the best guage of our promise to share
effectively the larger insights and relevance of our research with the public.
V. WORK PLAN, PERSONNEL, PUBLICATIONS, DATA PRODUCTS, EQUIPMENT, AND BUDGET
NOTES
Dr. Clark Chapman, as P.I., will oversee the entire research project. He will co-lead the low-res spectrophotometric
and lightcurve photometry portions of the project and will play a major role in the analysis, interpretation, and
synthesis of the data; he will commit 20% of his time to leading public outreach efforts. Dr. William Merline will lead
the adaptive optics observations, co-lead the lightcurve photometry, and contribute to reduction of all of the
observational data. Dr. David Nesvorny, who led the theoretical analysis that discovered exceptionally young families
and clusters, will participate in some observations and will lead the first-order interpretation of the data for the relevant
physical processes that we are exploring. Dr. Eliot Young will lead our moderate-resolution spectral studies using
NIRSPEC and co-lead the IRTF spectrophotometric observations; Dr. Young leads a NASA-funded project for IRTF
data reduction. Dr. Peter Tamblyn will lead the planning and coordination of our observing runs and will contribute to
data reduction. Our overseas Collaborator, Dr. Petr Pravec, is one of the world's most productive lightcurve observers
(cf. Pravec et al. 2002) and will obtain many of the proposed lightcurves. Drs. Merline, Nesvorny, and Young will
also contribute to the public outreach efforts led by Dr. Chapman.
We expect to work more-or-less continuously on all observational tasks throughout the three years, emphasizing
analysis, synthesis, and publication in the third year. As is true of most observing projects, we cannot be assured in
advance that we will get telescope time (or be rewarded with working equipment and clear skies), but we have an
excellent record of obtaining time (and making good use of it!) on the most competitive telescopes in the world. For
example, Dr. Merline (generally with co-I Chapman) has been awarded time (often multiple observing runs) during the
last several years on HST, Keck, Gemini, CFHT, Mt. Wilson, and Palomar. Dr. Young has been a frequent observer
on the IRTF; he has also had several Keck/NIRSPEC runs. Drs. Chapman and Merline have frequently used numerous
facilities in Arizona (e.g. the Vatican Observatory and KPNO telescopes), and will arrange to use nearby telescopes in
Arizona, Colorado, and/or New Mexico for purposes of our lightcurve observations. (Since telescope allocations are
made in TAC processes wholly divorced from this proposal, we cannot know now when we will get time, so we
obviously cannot detail our observing or work schedule more precisely.)
12
Our travel budget supports 13 formal observing runs. The facilities are carefully chosen to yield maximum
scientific return at lowest cost. We budget 5 trips to IRTF, and within each run we combine our SpeX and MIRSI
goals so as to avoid additional travel. For each facility we budget travel for 2 observers for only the first trip to that
facility for this program. We firmly believe that this is required for efficiency, to prevent overloading one observer in
starting this new program, and to refine observing and reduction techniques. Subsequent runs will be made by just one
observer, which should be adequate once we know our routine. Indeed, we hope to take advantage of remoteobserving opportunities (e.g. at IRTF), but we cannot judge whether they will suffice for our challenging program; thus
we conservatively budget for these trips, while hoping that we can eliminate the costs for some trips in this way (our
budget does take account of the fact that some observatories pay for some or all travel expenses; e.g. NASA/Keck time
now comes with nearly full travel funds). In any case, we will have additional observers on-line, in real-time, from the
home institution during most runs, to assist decision-making and data reduction. Our remaining travel is very modest:
3 scientific meetings; actual travel costs will be determined by the market, but we are obliged to budget them under
current prices and guidelines. In addition to these trips, we will perform, with no travel costs, multiple "runs" using
the Univ. of Colorado facility (<2 miles from the SwRI office) to acquire lightcurve data on brighter targets; such
observations are not technically demanding. We will also be assisted by Collaborator Pravec, who will acquire
lightcurve data at no specific cost to this project.
We seek support for a total of 3 meeting trips for one person to present our results. We budget these as one DPS
meeting in the second year (it is in the U.K.); in the 3rd year we budget one DPS meeting and one AGU meeting. The
required labor is calculated to allow coverage of planning (1 day per run), travel (1-2 days per run depending on
location), making the observations, and data reduction (time equivalent to the sum of planning, observing, and travel
for that run; e.g. a 7-day run requires ~7 days of data reduction). Thus planning, observing, and data reduction
consumes about half of our labor allocation. The remaining 50% is allocated to local lightcurve observations, firstorder data analysis and interpretation, presentation of the results at meetings, archiving our data (perhaps in the PDS
Small Bodies Node, but certainly on a publicly-available website), and publications in peer-reviewed journals; note
that SwRI will pay any page charges for these publications. We will regularly report progress at professional meetings
and colloquia and will promptly publish our data and, eventually, our interpretations in the peer-reviewed literature,
once we have reduced sufficient subsets of data or reached important insights.
We require no funds for observational instrumentation or equipment and have no archived data requirements.
SwRI provides all computer hardware, software, routine computer support, and data storage capabilities. We call
attention to the "Science Proposal Budget Notes and Institutional Contributions at Southwest Research" in the budget
section, which explains in part how -- in spite of the appearances of the unusual accounting procedures that we are
mandated by government auditors to use -- our budgeted work is actually very cost-effective.
VI. RESULTS FROM PRIOR NSF SUPPORT
The P.I. has received no NSF support during the past 5 years. Results from NSF awards for two Co-Is (Drs.
Nesvorny and Merline) are reported below.
Dr. David Nesvorný. NSF Award #0307926. Formation of Kuiper Belt Binaries and Planetary Satellites. $60,572 per
year from 07/01/03 to 06/30/06 (continuation of NSF award #0074163, Dynamical Studies of Planetary Satellites).
This award resulted in 6 publications in refereed journals, several conference talks, press communications and public
lectures. Our results include: (i) Present systems of satellites at Uranus and Neptune are only compatible with much
less planetary migration than suggested by previous studies. (ii) A study that revealed the importance of collisions
between irregular satellites of the Jovian planets with implications for imaging of Phoebe's surface during Cassini's
close flyby in June 2004. (iii) Year 2002 prediction that Trojans of Neptune exist; the first Trojan of Neptune, 2001
QR322, was discovered in early 2003 by the Deep Ecliptic Survey -- a survey that uses the National Science
Foundation's telescopes at Kitt Peak National Observatory in Arizona and Cerro Tololo Inter-American Observatory in
Chile. (iv) Identification of dozens of asteroid fragments from the most recent catastrophic collisions that occurred in
our solar system. The 6 publications are: Beauge et al. (2002) and Nesvorný et al. (2002a, 2002c, 2003a, 2003b,
2003c).
13
Dr. William J. Merline. NSF Award AST9802030. A Ground-based Search for Asteroidal Satellites using Adaptive
Optics. PI: William J. Merline, Co-Is: Clark R. Chapman, David Slater. 10/1/1998-9/30/2001, total funding: $99,961.
And NSF Award AST98726. Search for Asteroidal Satellites Using Adaptive Optics. PI: William J. Merline, Co-Is:
Clark R. Chapman, David C. Slater; Other Professionals: Laird Close, Christophe Dumas, Chris Shelton, Francois
Menard. 10/1/2001-9/30/2004, total funding $136,292.
These two projects embarked on the first dedicated survey of a large number of asteroids (hundreds) for the presence
of satellites. They resulted in the detection of the first known asteroid satellite from Earth (HST or ground-based)
when 45 Eugenia was found to be binary in 1998. It was only the second known binary, after 243 Ida. This team has
now discovered 11 of the 16 known binaries among the main-belt and Trojan asteroids. Among the "firsts" are the
detection of the first (and only) true double asteroid (components of the same size) (90 Antiope), the first and only
Trojan binary (617 Patroclus), and the first binary thought to be formed by a catastrophic collision of the type sought
in this proposal (3749 Balam). We now see that at least 3 mechanisms must be responsible for formation of the
main-belt binaries, and the observed systems appear to be falling into well-defined clusters of parameter-space
characteristic of these formation mechanisms. We also see differences in characteristics and frequency between
C-type and S-type systems. Our survey has studied >600 asteroids; the binary frequency among main-belt asteroids is
low, ~2%. Our work has permitted determination of the densities of some primary asteroids (in binaries); we find that
all C-types have densities 1.0-1.5 g/cc. Major publications resulting from our work include Merline et al. (1999c) and
Merline et al. (2002b), along with many IAU Circulars (e.g. Merline et al. 2002a, 2003a).
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Figures and captions to be moved up into text:
Fig. 1 New test-of-concept simulations of catastrophic disruption, at scale of Karin cluster creation. Shows the system 35 min. after
a 3-km impactor collides with a 25-km target, at 5 km/s, with impact parameter 0.26 target radii (impact angle 15º). A collaborative
Artificial Intelligence computational effort of SwRI and JPL (involving Co-Is Merline and Nesvorny, P.I. Chapman, among others at
SwRI, using modeling codes of E. Asphaug and D. Richardson).
18
Fig 2. Major asteroid families in the main belt. All currently known members for each family are plotted in aP,eP projection. Symbol
size reflects asteroid size. Some families are more tightly clustered, perhaps reflecting recent breakups. The Veritas family at 3.17
AU has an especially small spread in aP, which contrasts with much larger spread of the Koronis family at 2.9 AU. These two families
correspond to breakups of two similarly-sized parent bodies (Marzari et al. 1995, Tanga et al. 1999). The Koronis family has been
dispersed by the Yarkovsky effect over ~2-3 Gy (Bottke et al. 2001). We also show several mean motion resonances (dashed lines),
and a well-known "secular resonance" (Williams 1969) involving Saturn.
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Fig. 3. The Karin cluster's orbital structure implies a recent asteroid break-up: (a) aP,eP and (b) aP,iP. The size of each solid symbol
reflects the diameter of a cluster member. Small x’s are background Koronis family bodies. The ellipses show the orbital elements of
test bodies launched at 15 m/s. The good match between ellipses and the observed cluster indicates that it must be <10 My old -otherwise the dynamical dispersion that modified other known families would prevent a good match (Nesvorný et al. 2002).
.
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Fig. 4. The convergence of angles at 5.8 My ago means that the Karin cluster was created by a parent asteroid breakup at that time.
The plot shows past orbital histories of Karin members: (a) nodal longitudes and (b) perihelion arguments. Values relative to 832
Karin are shown. At 5.8 My ago (broken vertical line), the nodal longitudes and perihelion arguments converge.
Fig. 5 from NASA PAST proposal
Fig. 5. The convergence of nodal longitudes at 8.3 My ago suggests that the Veritas family was formed by a catastrophic collision at
that time. The bottom plot shows past orbital histories of nodal longitudes relative to 1086 Nata. The average nodal longitude (top
plot) of 40º at t=-8.3 My, is much smaller than at other times.
Fig 6 from NASA PAST proposal
Fig. 6. Discovery image of S/2002 (3749) 1, a satellite of asteroid 3749 Balam, acquired by Merline et al. (2002a,c) on Feb. 8, 2002,
using the Gemini Hokupa'a AO system. This asteroid/satellite system is similar to those we propose to discover. The primary is ~7
km diameter, the secondary 1.5 km (the size of Dactyl). If observed at 2 AU, this system would be about V=17, with separation 0.25
arcsec, well within the capabilities of the AO systems we propose to use. This system is the most loosely-bound system known,
even more so than the Kuiper Belt binaries, well beyond the Hill sphere. This is likely the first example of a binary asteroid created
during a catastrophic disruption; most other main-belt asteroid satellites orbit ~10 orbit radii and probably formed by other processes.
21
Fig. 7. Visibility of Karin (dotted) and Iannini (dashed) family members from a representative observing site (Mauna Kea), 1 July 2004
to 31 December 2007. Here, the large, bright asteroid 1379 Nele is included within the Iannini family, although that assignment is
uncertain; our observations may resolve whether or not it is an interloper. The horizontal lines (and the bottom of the plot) represent
approximate limiting magnitudes for the various types of observations proposed: V=16-17 for MIRSI, 17.5 for VLT AO satellite
searches, 18 for low-res. SpeX (current), and 19.5 for improved TCS SpeX; our nominal limits are 17.5 and 19.5 for lightcurve
photometry and 18 for Keck spectra. Visibility is assumed when the target has elevation >25 deg. and >15 deg. from the Moon.
Ticks on the horizontal axis indicate years and months. There are several oppositions for some targets during the 3.5 years
displayed. Such plots and tools we have developed are useful in planning telescope proposals in order to efficiently observe as many
targets as possible.
Fig. 8 from NASA PAST proposal (where it is called Fig. 7)
Fig. 8. Shown here is a pair of spectra taken recently by Co-I Young with NIRSPEC at R=2200. These spectra of the Centaur
Chariklo (Vmag = 17.79) were obtained in 2 consecutive 5-minute exposures at 2 different slit positions ("A" and "B"). We show the
A-minus-B pair here. The counts in either beam were ~170 DN above the background in 300 sec., or ~6 times the average
background of 27 DN.
22
***Need 1-page summary sheet, mentioning both intellectual/technical and broader merits, 3d person
***Need my 2-pg bio sketch (w collaborators)
***Things to be taken care of Friday:
Check for failure to convert special symbols (e.g. diacritical marks in Knezevic’s name [2nd parag of Tech
Background], symbols dealing with proper elements, etc.)
Alisha should try to format tables the way she did for NASA proposal.
Alisha could also try to save space by reducing the spaces between paragraphs from a full extra line space to perhaps
half an extra line space. I’ve spent half an hour trying, unsuccessfully to figure out Bill Gates silly linespacing/paragraph spacing controls.
There are specifications for margins, lines per inch, font-size, etc. I think I have these approximately set, but there
may remain issues (with the page no. footers, for example). We may have to compromise slightly, and I have done so
in selection of fonts for captions, line spacings within tables, etc. In particular, the margin on pg. 1 is too narrow
because I don’t know how to handle footers.
Eliot failed in his promise to get back to me last night about the limits for MIRSI. If the current V=16-17 is woefully
wrong, Bill & Eliot could try to change these. Also, I found that Eliot had failed to check some absurdly obsolete
statements about himself…I fear that Eliot’s checking of stuff is inadequate, and we are “winging it” on his stuff for
the third year in a row. If something can be done to double-check this stuff, it really should be.
I have the figures and captions at the end of the text. They should be moved up to within a page-or-so of where they
are first mentioned. Some of the figures are not available to me. They must be obtained from the NASA Planetary
Astronomy proposal. I will try to check late today that the figures have been inserted correctly.
David and others should check that the captions (especially for new figures) are correct. I found that they hadn’t been
changed when the new figures were made.
The references should be separated from the text and placed where required. It would be nice if someone could verify
that there are no old “submitted” or “in press”.
Alisha – Bill evidently can’t read Word documents. Please print a copy for him.
Alisha – double-ck that the page of budget explanations referenced in the final paragraph of Sec. V in fact exsits where
we say it does.
OK to shrink figures somewhat more (so long as still legible) to gain space.
23