Randii Wessen, PhD Speaks on “The Future of US Robotic Planetary Exploration” AIAA-LA-Las Vegas
Section, February 27, 2014
Jet Propulsion Laboratory (JPL) scientist Randii R. Wessen, PhD spoke on “The Future of US Robotic
Planetary Exploration,” an information-packed and lively presentation, to the Los Angeles-Las Vegas
Section of the American Institute of Aeronautics and Astronautics (AIAA) on February 27. His talk
covered the various robotics missions, from close up views of the Earth (mapping of climate, earthquake
stress patterns, atmosphere and water), then through the solar system (the Moon, lingering on Mars,
then other planets and asteroids) and beyond (the stars and exoplanets).
The evening’s events began as the AIAA Section events chair Christianna Taylor, PhD gave introductions
as attendees dined. She first introduced a group of students from California State University, Long
Beach, who announced their upcoming event on April 10, which is listed in The Odyssey’s calendar. Dr.
Taylor then introduced Dr. Wessen.
Wessen described the beginning of JPL as a military program, and then as part of the California Institute
of Technology. He explained that the students needed some place less populated than Pasadena in
which to test rockets, so they opted for the Arroyo Seco. Then NASA became involved, or as he put it,
“they pay Caltech to run JPL.” JPL scientists designed, built and operated Explorer 1, which in 1958
became the first satellite successfully launched by the United States. Wessen showed a photo of thenJPL director William Pickering, scientist James Van Allen, and rocket pioneer Wernher von Braun holding
up a model of the satellite during a press conference after the launch. “Jimmy’s in the middle,” said
Wessen, and yes, he is that Van Allen—the Earth radiation belt discoverer, thanks to instrumentation he
built for Explorer 1.
Today, JPL covers 177 acres and has 177 employees – 1/3 have PhDs and 1/3 have master’s degrees.
Wessen described how JPL controls the Deep Space Network, of which there is always one antenna that
sees a given spacecraft, and then told about described JPL’s constellation of Earth-observing spacecraft.
He showed an interferometer image of Los Angeles earthquakes, a profile of ocean surface salinity from
the Aquarius/SAC-D space-based observations, Aura’s Earth Observing System Microwave Limb Sounder
ozone hole imaging, and a graph of the atmospheric carbon dioxide levels increasing from 1950-2006.
SMAP (Soil Moisture Active Passive) imaging showed soil moisture freeze-thaw cycles, an important
factor in weather and climate change. Wessen then made a quick stop on the Moon, with a video of
ATHLETE (All-Terrain Hex-Legged Extra-Terrestrial Explorer) stepping off the Altair lander.
And then it was on to Mars, on which he went into great detail. He began with images of water
channels, and also mentioned the presence of water vapor in the Martian atmosphere. Topography
maps showed higher altitudes in the south than in the north; the southern high plateaus are covered in
craters, in contrast with the northern plains. This led to speculation on whether an ocean could have
covered the lower, flatter north.
This year marks the 10th anniversary of Spirit and Opportunity landing on Mars: Spirit lasted 7 years, and
Opportunity is sending data to this day. Opportunity arrived at the Endeavour Crater in 2011, a journey
of approximately 7 miles from its last investigation point (the Victoria Crater) and more than 13 miles
since it landed on Mars. Remarkable indeed for a rover originally designed to travel only one kilometer!
The Endeavour Crater was chosen because the Mars Reconnaissance Orbiter’s detection of clay minerals
within the crater suggested that Mars may have been a much warmer and wetter place. In addition,
within the 22-km diameter crater—over 25 times wider than Victoria—far older layers of bedrock would
be exposed, dating back to the Noachian period (3.7-4.1 billion years ago). However, within the larger
and hence steeper crater, Opportunity would have been at greater risk of falling. But the rover and its
sister had gained an advantage: autonomous driving software uplinked in 2006 uses stereo images from
the High Resolution Imaging Science Experiment camera to generate 3-dimensional terrain maps, which
are in turn used to determine the safest route for the rover. Autonomous control has enabled Spirit and
Opportunity to travel further and more quickly than would have been possible with step-by-step
directions from Earth.
Since Spirit and Opportunity are solar powered, the Mars Ops team needs to keep Mars time. A Mars
day, or “sol” (as Wessen put it, “did you do that yestersol?”) is about 40 minutes longer than an Earth
day. This led to comments on the investigators becoming “permanently jet-lagged”.
Wessen went on to describe findings of water. Water ice was found in craters in the lower latitudes. He
also showed pictures of lines leading down the inner slopes of Newton Crater that appear and disappear
with the seasons. These lines are suspected to be salty liquid water.
Next, Wessen took the audience forward to the landing of the Mars Science Laboratory in August of
2012. The audience was treated to a showing of the exciting 7 Minutes of Terror video, in which years
of planning culminated in the most complex set of landing maneuvers yet performed: guided entry,
parachute descent, powered descent, and rocket-powered sky crane. He then showed the MSL landing
site near Mount Sharp, Gale Crater’s central peak rising 3 miles above the crater floor. Mount Sharp,
formed by the deposit of multiple layers of sediment after the crater impact, is expected to contain
information on at least a billion years of Martian geological and climate history.
Wessen next described another mission, Mars Atmosphere and Volatile EvolutioN (MAVEN), which will
examine the loss of the Martian atmosphere. Mars lost its magnetosphere billions of years ago and with
it the ability to retain its atmosphere; evidence supports its having been stripped away by the solar
wind. MAVEN, on track to arrive at Mars in September 2014, will investigate the effects of solar activity
on what remains of the Martian atmosphere. Still another mission, Interior Exploration using Seismic
Investigations, Geodesy and Heat Transport (InSight), will analyze Mars’ interior to uncover how the
planet—and presumably how other rocky planets—formed.
Another Mars rover mission is under consideration for launch in 2020. This may be a sampler mission
equipped with a cache canister for a possible return to Earth in a future mission. Core samples could tell
of subsurface life.
Next, Wessen touched on missions to the rest of the solar system. First he described findings from the
Cassini mission to Saturn and its moons. A photo showed how Saturn fits into the distance between the
Earth and the Moon with its ice rings extending further, and that the rings are a mere 150 feet thick.
Titan has an atmosphere of 95% nitrogen versus Earth’s 78%, with approximately 1.5 times Earth’s
atmospheric pressure; this led to speculation on whether a much younger Earth could have had a similar
atmosphere. Titan also features liquid methane and ethane in a slow rainfall, where ice forms at the
bottom of the lakes (unlike what happens with water ice, which is less dense than liquid water).
Rounding of rocks on Titan also indicated erosion. Wessen then mentioned Saturn’s moon Enceladus
and its surrounding water vapor, calling it “Cassini Carwash”. Wessen briefly mentioned several other
missions: Mercury MESSENGER, the first spacecraft to orbit Mercury; New Horizons, due to reach Pluto
by mid-2015; Juno and the Europa Jupiter System Mission; and Titan Saturn System Mission Concepts.
Juno will study Jupiter’s radiation belts, magnetic fields and atmosphere to further the understanding of
the planet’s origin and evolution, but will travel in a polar orbit to minimize exposure to the damaging
levels of radiation. The Europa Jupiter System Mission Concept would focus on Europa, Ganymede and
Jupiter’s magnetosphere, to determine whether Europa could harbor life, given what we know about
the presence of water, organics, and energy. The Titan System Concept goal is to understand Titan’s
evolution, which could inform about Earth’s; the mission would include an orbiter, a balloon and a lake
lander.
Wessen went on to tell about recent asteroid discoveries. It turns out that some asteroids even have
moons. The Galileo spacecraft made the first discovery in 1993: a tiny moon, Dactyl (1 mile in diameter),
orbiting the asteroid Ida. Wessen followed this with information about the Dawn mission, which
reached Vesta using ion propulsion back in 2011 and left for Ceres in 2012. A projected image compared
the two: Ceres, at nearly twice the diameter and three times the mass of Vesta, is the largest of the
asteroids and was recently designated a dwarf planet. In January 2014, water vapor was sighted around
Ceres - the first-ever such sighting of water vapor. The Dawn mission aims to arrive there in 2015.
Wessen then outlined another, upcoming, asteroid mission: OSIRIS-Rex (Origins Spectral Interpretation
Resource Identification Security -- Regolith Explorer), scheduled to launch in 2016 to visit the asteroid
Bennu and remove a sample. Analyses will tell us more about the materials in the formation of the solar
system, as well as possibilities for asteroid mining. Further information may come from a proposed
and far more ambitious project: capturing a Near Earth asteroid and placing it into lunar orbit.
Astronauts and robotic probes could study this asteroid far more easily than traveling further to Near
Earth asteroids.
The asteroids include over 400,000 minor planets, which include 5,200 Near-Earth objects—900 of them
potentially hazardous. Wessen’s example was the comet Shoemaker-Levy 9, which broke apart and
collided with Jupiter. The collision of one of the fragments released the energy of 6 million megatons of
TNT. Wessen compared this to one A-bomb dropping per second for 11 years!
So where did we come from? Astronomers are answering this question by looking for the oldest
formations of stars.
He showed an image of the Orion constellation as detected in the infrared, visible, ultraviolet, and X-ray
spectra to show different aspects. He showed the Eagle nebula with its star nurseries in the “Pillars of
Creation”, 7,000 light years away. While gas and dust are forming new stars, nearby hot stars already
formed are eroding them with UV radiation. Next, Wessen showed images from the Spitzer Space
Telescope of new stars forming in a galaxy. This was followed by a voyage back in time: the HubbleUltra Deep Field Photo was taken with a long exposure (11.5 days), pointed at a small area of the sky
chosen because it appeared empty of stars. This would optimize detection of the faintest, presumably
farthest, galaxies. This showed the deepest optical view in space: formation of the earliest galaxies,
roughly 500 million years after the Big Bang.
And where do we go from here?
The Kepler mission has located earth-like planets through the observation of star transit events. So far,
3,538 exoplanets have been identified and 941 confirmed, 647 are Earth-sized…and 24 are in inhabitable
zones. To increase the detection of exoplanets, the proposed New Worlds Mission would consist of a
space telescope flying in formation with an occulter, or “starshade”, to block the light of stars that
would otherwise obscure our detection of their orbiting planets.
So WHY are we doing this research?
Wessen’s last slide showed the answers:
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Exploring Our Universe
Understanding Our Planet
Improving Our Lives
Wessen concluded with a quote from K.E. Tsiolkovsky, the Russian father of rocketry: “The Earth is the
cradle of mankind, but mankind cannot live in the cradle forever”.