EXECUTIVE SUMMARY
INTRODUCTION. Astrobiology is a 21st
century endeavor with virtually unparalleled
scientific promise and public appeal. NASA has
capitalized on the promise of astrobiology by
forming the National Astrobiology Institute
(NAI). We, the Southwest Astrobiology Center
(SWAC), are excited to propose to join the NAI
as a new lead center.
This Lead Team proposal focuses on
exploring,
and
ultimately
significantly
expanding, [note comma] the presently limited
notion of Habitable Zones (HZs) where waterbased life can exist. In doing so, we will break
new ground regarding what habitability means
in many important areas. For example, we will
study the longevity of oceans on planets
surrounding stars of various types, the role of
heavy bombardments long after planetary
system formation and initial clearing is
complete, the importance of stellar and galactic
radiation events, and the possibilities of cave
and cloud life on planets with inhospitable
surfaces.
To accomplish these goals we have brought
together an internationally recognized team of
experts in planet formation, astrophysics,
planetary climate modeling, and the study of
biological
refugia.
We
believe
this
multidisciplinary team is a distinguishing
strength of our proposal.
Further, we have marshaled considerable
internal resources to augment and supplement
the budget proposed here to the NAI, so that
SWAC will be an attractive, well-leveraged
investment by the NAI and NASA. So, [comma]
too, we propose an exciting and intensive
Education and Public Outreach (EPO) effort,
which includes broad participation across our
team’s Midwest/southwest geographical area
(Texas, Missouri, Colorado, and New Mexico),
as well as targeted efforts involving minority
and underrepresented institutions. These and
other aspects of our proposed Lead Team effort
will all be carefully managed under the direction
of PI David Grinspoon and the Department of
Space Studies (www.boulder.swri.edu) of the
Southwest Research Institute (www.swri.edu).
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SCIENTIFIC FOCUS & THEME. In the
astrobiological literature it has become common
to refer to a “habitable zone” (HZ) around a star
as the region of space where the conditions are
favorable for our kind of life. This was
classically defined as a range of astrocentric
distances where stable bodies of liquid water can
exist at the surface of a planet (e.g., Huang
1960; Rasool & DeBergh 1970; Hart 1978).
One dimensional climate models have since
been brought to bear on the problem of
calculating the spatial limits of stellar habitable
zones for Earth-like planets with CO2/H2O/N2
atmospheres (e.g., Whitmire et al. 1991; Kasting
et al. 1993). Although these and other pioneering
investigations explored the limits of HZs for a
range of stellar types, they were highly limited
in that they did not consider many other factors
[delete comma]. Such factors include the
incredible diversity of orbit stability, planetary
sizes, stellar types, impact histories now widely
expected to be prevalent in the galaxy.
Our primary objective is to widen the concept
of Habitable Zones by exploring a wide range of
quantitative issues that have either been ignored
or insufficiently explored so far. Our secondary
objectives are to help guide the design
requirements and operational target selection
planning
for
extra-solar
planet
detection/exploration missions ranging from
Kepler to the Terrestrial Planet Finder (TPF). In
addition, we will contribute to broadening the
scientific base of the astrobiology community
[what does this phrase really mean?], and
provide a deep and meaningful education and
public outreach effort.
Of course, no group could realistically
examine every possible variant on habitability in
a proposal of the scope feasible for the NAI (for
example, in our work we will not consider
chemistries relying on solvents other than H2O,
and we will focus primarily on worlds where
liquid water can exist). With these pragmatic
limitations in mind, we will, however, explore in
detail a wide range of important issues that have
limited the concept of planetary habitability.
These include:
 Which types of stars form rocky planets,
and how do the giant planet architectures of
systems affect the habitability of the terrestrialclass (i.e., 0.01 Earth-mass (i.e., Europa-mass)
[? Parentheses not parallel] to 2 Earth-mass)
worlds residing in stellar HZs?
 How do variations in galactic chemistry
(C/O, Si/Fe), stellar type, planetary size and
volatile inventory affect the formation
frequency, structure, and evolution of solid
planets? How does the coupled climate/surface
evolution of solid planets affect their ability to
retain oceans and support life?
 How does a star’s path through the
inhomogeneous and occasionally hazardous
galactic environment promote (and limit)
biological evolution on its planets?
 What is the nature and viability of biota
that may have been forced to seek refugia (e.g.,
in caves or high clouds) from damaged or
destroyed surface-biospheres?
Our work to address these and other questions
related to our goal of exploring the limits of
planetary habitabilitywill be organized into four
separate but interrelated investigation themes.
These are:
1. The origin of water-bearing terrestrial
worlds.
2. The geophysical and atmospheric evolution
of water-bearing terrestrial worlds over time.
3. External influences affecting habitability of
water-bearing terrestrial worlds.
4. Refugia for water-based life in cloud and
cave environments.
Within each theme we will undertake the
development and exploitation of a suite of
sophisticated models; in some themes we will
also undertake a variety innovative field
experiments.
Results will be tested against existing data on
the history and characteristics of Earth and other
Solar System planets. The rapidly growing
dataset on extrasolar planets will also be
employed to help constrain and test the results
from our projects.
Once developed and tested, our state-of-theart models will be offered to the wider NAI
community as tools for general use [I am very
skeptical of such promises…suggest removing
this lightning-rod promise]. Similarly, as we
take biological field experiments to relatively
unexplored frontiers of Earth’s biosphere to shed
light on the limits of life’s domain, we will
invite the participation of other NAI institutions
and individuals.
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OUR TEAM. To accomplish the broad
range of research proposed here, we have
assembled
an
outstanding,
highly-[omit
hyphen]productive, interdisciplinary PI/CoI
team of 15 experts from 6 separate institutions.
Our team has deep experience in fields
including: celestial dynamics, planet formation,
and astrophysics (Levison, Dones, Bottke,
Danly, Scalo), planetary atmospheres and
climate evolution (Grinspoon, Bullock, Pavlov),
planetary geology and geophysics (McKinnon,
Chapman, Durda), microbiology (Boston,
Sattler), and biospheric modeling (SchulzeMakuch, Irwin). Over 40 refereed publications
have already been authored by members of this
team working together in various subgroups.
This CoI team will be assisted by a group of 9
scientific collaborators from a various additional
institutions. The team of CoIs and Collaborators
assembled in our Lead Team proposal will be
led by Dr. David Grinspoon, an expert in the
climate evolution of terrestrial planets. PI
Grinspoon is an internationally recognized
scientist and author, known for his broad but
penetrating approach to interdisciplinary
problems.
COMMUNITY BUILDING. Although our
primary focus will be as a research center,
significant effort will be expended in community
building. This will include student training,
postdoc mentoring, and EPO activities. In total,
it is expected that 4 multi-year postdocs will
reside in SWAC during the 5-year funding
period. Further, 5 or more grad students and 5
visiting summer scientist positions are also
budgeted. Our first visiting scientist will be Dr.
Jim Kasting of Penn State, anexpert in climate
change. Other external science community
members will interact with SWAC via a series
of video-broadcast seminars and annual
workshops we will host on focused topics
related to our four research themes. The first of
these workshops will be held in the winter of
2003 in Boulder; it will focus on the longevity
of planetary oceans.
INSTITUTIONAL COMMITMENTS. The
Southwest Astrobiology Center (SWAC) will be
formally housed within the Southwest Research
Institute’s Department of Space Studies, located
in Boulder, Colorado.
The Southwest Research Institute (SwRI) will
support SWAC with over 2000 ft2 of physical
space and furnishings, phone/LAN/wireless, and
various computing and laboratory facilities,
none of which will be charged to this project. In
order to further leverage the value of this effort
to NASA and the NAI, SwRI is also providing a
direct cost share to this 5-year proposal of $K,
and some $90K in capital equipment for a pair
of high-speed computing clusters. SwRI will
also sponsor, at its own expense, annual, topical
science workshops in Boulder to facilitate
collaboration between our team and the wider
astrobiological community. Additionally, the
other academic team member institutions of
SWAC will provide institutional commitments
in the form of academic year salaries, office
space, and computational facilities. The Denver
Museum of Natural History and Science will
provide extensive in-kind EPO support.
EDUCATION & PUBLIC OUTREACH.
An ambitious program of Education and Public
Outreach (EPO) will be implemented both to
share the general excitement of astrobiology and
the specific results of our research. We will
reach a broad audience of students, teachers,
families and the general public. Numerous
members of our PI/CoI team are already
recognized as creative educators and visible
public spokespersons for space and biological
science.
Our EPO efforts will involve a suite of
productions, presentations, and planetarium
shows.
We will also provide innovative
documentation of the process of devising and
implementing a multidisciplinary astrobiology
program, in the form of an ongoing radio series
reporting on our team, our science,[add comma]
and our progress. We will also undertake an
innovative program of teacher training to
leverage our efforts and reach the widest
possible number of students. In keeping with
our regional focus on the Southwestern U.S.,
large components of our EPO program will
focus on teaching underserved students in the
Hispanic and Native American communities.
Through support of graduate and undergraduate
students at four of our member institutions, we
will contribute to training the next generation of
astrobiologists. All of our EPO efforts will
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involve measurements to evaluate progress and
improve the products being delivered.
MANAGEMENT APPROACH. PI Dr.
David Grinspoon will be accountable to the NAI
and responsible for managing our research and
EPO programs.
Dr. Grinspoon [duplicates
words on previous pg] has managed numerous
NASA grants as PI and served on various NASA
advisory committees, including most recently
SSES.
As described above, the research to be
performed within SWAC will be divided into
four theme areas. Each research theme, and our
EPO effort, will be led by a specific CoI. In
addition, a Steering Group, consisting of the
theme team leads will meet annually to advise
the PI on SWAC strategic and management
issues. The SWAC Steering Group (SSG) will
be chaired by collaborator Dr. Alan Stern,
Director of the Department of Space Studies at
SwRI.
Using established schedule and cost tracking
tools (Microsoft Office) regularly used at SwRI,
Dr. Grinspoon and administrative assistant Ms.
Alisha Bouliche will track and manage the
spending and progress of all of the research,
training, and EPO activities within SWAC.
CODA. It is human nature to seek other
warm spaces. NASA is doing just that with the
Terrestrial Planet Finder (TPF) and related
missions, as well as via the research funded
through the NAI. Our proposed contribution is
to dramatically deepen what is known about the
conditions under which planetary bodies can
evolve to and sustain habitablility.
We believe this topic has [“to-date” is NOT a
word!] not yet been fully exploited
intellectually, resulting in a “handicapped”
understanding of what habitability means and
the range of conditions and locales that may
actually be habitable in our galaxy. By focusing
an intensive, 5-year effort on this topic, we seek
to offer the NAI a major advance in
understanding how common life may be.
LIST OF EXEC SUMMARY FIGURES:
Org Chart
Project Schedule (ala Meadows)
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RESEARCH AND MANAGEMENT PLAN
RESEARCH PLAN OVERVIEW
What kinds of planets can support life in the
universe? A widely held belief, based (by
current practical necessities) on the terrestrial
example, is that to support life, a planet should
have stable bodies of liquid water. This has in
turn led to the conventional notion of a habitable
zone (HZ) as a range of distances from a star
where water can exist on the surface of a solid
planet for biologically relevant timescales.
We propose here an exciting and, we think
overdue, interdisciplinary research program to
deeply explore the full range of planetary
settings where this requirement can be met[omit
comma]. This will expand the notion of
terrestrial planet habitable zones beyond the
range of stable surface liquid water.
Our research program into the general
question of terrestrial planet habitability is
divided into four closely related Themes.
In theme 1, Forming Terrestrial Planet
Systems, we will simulate the formation and
evolution of terrestrial planet systems over a
wide range of realistic starting conditions that
likely obtain across the galaxy. Our goals are
twofold: we intend to determine (i) how the
chemical composition of planet-forming
material, which varies both temporally and
spatially within our galaxy, affects the types and
number of planets formed, and (ii) how other
critical factors like stellar mass, luminosity, and
proto-planetary disk mass determine the ability
of planetary systems to form stable, habitable
terrestrial planets. A crucial goal, as described
later in detail, will be the determination of the
expected water abundance of worlds after
accretion and outer solar system clearing is
complete.
We will accomplish this work using state-ofthe-art models of planet formation, orbital
stability, and impact fluxes, developed by team
members with extensive experience in these
very areas of research [rewrite previous
sentence: WHAT will be buttressed? What does
“buttress” mean? What will they DO, as distinct
from what do they “understand”]
We will build upon these results in theme 2,
Diversity and Evolution of Rocky Planets. Using
the planetary system formation results produced
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in theme 1 and existing state-of-the-art planetary
formation models and coupled, climate-ocean
models, we will study (i) the thermal evolution
of planets and their atmospheres as a function of
size and chemical composition; (ii) the diversity
of atmospheres of surrounding such planets; and
(iii) the astrobiologically-crucial issue of the
longevity of oceans on planets as a function of
astrocentric distance and stellar type.
Our third theme, “Surface Effects and
Refugia from Stochastic Perturbations to
Habitable Conditions,” will be devoted to
understanding
the
effects
of
several
astronomically mediated episodic processes
which can alter planetary environments. These
processes present both threats and opportunities
for biological survival and innovation. These
perturbations include episodes of intense
radiation due to stellar flare activity, [always a
comma before “which”] which, as described
below, we now believe to be a more common
source of planetary radiation spikes than
“cosmic explosions” such as supernovae and
gamma-ray bursts. We will perform the first
realistic simulations of a planetary system’s path
through the variable interstellar medium,
allowing us to model the climatic and genetic
effects of inevitable passages through dense
molecular clouds, including enhanced cosmic
rays due to astrosphere collapse, enhanced UV
due to stellar H accretion, and climate cooling
due to increased dust accretion. In this theme,
we will also model climate perturbations caused
by large impact events and possibly very severe
“Very Late Heavy Bombardments” (VLHBs),
caused by late dynamical instabilities in a
planetary system.
In theme 4, “Expanding the Habitable Zone:
Refugia,”[previous sentence is completely
garbled – what are we trying to say?]. In
particular, we will use models and empirical
studies to determine the ability of cave and
cloud environments on terrestrial planets to act
as refugia during these excursions from surface
habitable conditions, helping to perpetuate life
on planets where it might otherwise be
extinguished. We will accomplish this via an
integrated set of field, laboratory, and theoretical
investigations to explore these highly important
and under-studied areas of planetary habitability.
As a part of this effort we will undertake field
expeditions in caves and we will sample clouds
to study their biology. Unlike other subsurface
realms studied by the NAI (sea-floor sediments,
thermal vents, deep igneous rocks), caves offer
the prospect of protecting or even promoting the
development of complex, metazoic life. In this
effort we will undertake a program of targeted
mountain expeditions and flight experiments
designed to characterize the biota in a range of
cloudy and upper atmosphere environments.
These results will be applied to biospheric
modeling of possible cloud-based life on other
planets. [better say a word here that life in
terrestrial clouds exist, that we have an expert on
that as a Co-I, in order to dispel initial thoughts
of reviewers that cloud life is crazy] These
explorations of the upper and lower limits to
habitability on Earth, and the modeling efforts
which they will support, will test and extend our
knowledge of the limits of planetary habitable
zones.
Our Tasks Bear Directly on Many of the
Goals of the NAI.
NAI Goal
Applicable
SWAC
Tasks
1 2 3 4
1. Understand the Nature
and Distribution of
Habitable Environments
X X X X
2. Explore for Past or
Present Habitable
Environments
X X X
3. Understand How Life
Emerges
4. Understand How Past
Earth Life Interacted with
Its Changing Environment
X X
5. Understand the
Evolutionary Mechanisms/
Environmental Limits of Life
on Earth
X
6. Understand the Principles
that Shape the Future of Life
on Earth and Beyond
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X
6
7. Determine How
to
Recognize Signatures of Life
X X X
INSERT
HERE
A
TABLE
RESEARCH OBJECTIVES
WITH
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