Vision and Voyages for Planetary Science in the - Solar System ...

detected in time. The report concluded that there were two approaches to completing a congressionally
mandated survey of hazardous objects. The more expensive but more expedient method requires both a
space-based survey telescope and a suitable ground-based telescope (i.e. a telescope capable of both
detecting relatively dim objects and also possessing a wide field of view enabling it to survey large
portions of the night sky). The more cost-effective method could be accomplished with a suitable
ground-based telescope over a longer period of time, provided that non-NEO programs primarily paid for
the telescope.
The 2010 astronomy and astrophysics decadal survey report New Worlds, New Horizons in
Astronomy and Astrophysics ranked the Large Synoptic Survey Telescope (LSST) as its top-priority
ground-based telescope, stating that it “would employ the most ambitious optical sky survey approach yet
and would revolutionize investigations of transient phenomena.” 67 The LSST was given first priority as
“a result of its capacity to address so many of the identified science goals and its advanced state of
technical readiness.” From the perspective of planetary science, the LSST will yield a rich new data base
that can not only be mined to search for hazardous near-Earth objects but would also be of major
scientific value in advancing primitive body exploration extending out into the Kuiper belt.
Although impact hazards to Earth are real, they are probably actually reduced by the gravitational
influence of the giant planets, especially Jupiter. Astronomical surveys tally the number of asteroids
larger than a kilometer at about a million. But, comet nuclei this size and larger are probably far more
numerous. When these objects are deflected into elliptical orbits that would bring them close to Earth
they often also cross Jupiter’s orbit. Simulations with large samples of orbital encounters show that
Jupiter deflects some on harmless trajectories that cross into the inner solar system, and that most are
ejected out of the solar system. In aggregate, then, Jupiter protects Earth. 68
Since the remarkable prediction of the impact of Shoemaker-Levy 9 with Jupiter in 1994 we have
witnessed three new jovian impacts as of this writing, one in 2009 and two in 2010. 69 The orbits and
impact rates of Jupiter impactors provides new information to understand how Jupiter deflects hazards
toward or away from Earth. Therefore continuous monitoring of Jupiter to capture these events would be
invaluable. Today, such work relies on a small number of highly motivated amateur observers; these
unfunded volunteers, however, cannot cover Jupiter at all times. Small, dedicated automated planetary
monitoring telescopes would be of great value in providing comprehensive surveys to capture future
impacts into Jupiter.
Can Understanding the Roles of Physics, Chemistry, Geology, and Dynamics in Driving
Planetary Atmospheres and Climate Lead to a Better Understanding of Climate Change on Earth?
Venus, Mars, Titan, Jupiter, Saturn, Uranus, Io, Pluto, Neptune, and Triton display an enormous
range of active atmospheres that in many respects are far simpler than that of Earth—an arguably more
difficult atmosphere to model and to understand. The interactions of Earth’s atmosphere, biosphere,
lithosphere, and hydrosphere present extremely complex, even chaotic, problems that defy our ability to
reliably predict their future or derive their past, either on short or long timescales. Venus, Mars, and Titan
provide atmospheric laboratories that exhibit many Earth-like characteristics but operate across the
spectrum of temperature, pressure, and chemistry. Likewise, giant planet atmospheres are also in many
respects much simpler to understand than is Earth’s. The processes that drive thick atmospheres can be
modeled without the complication of a liquid or solid surface.
Consideration of the full suite of planetary atmospheres immensely broadens the scope of
atmospheric science. The goal to understand the full spectrum of planetary atmospheres—the physics,
chemistry, dynamics, meteorology, photochemistry, solar wind and magnetospheric interactions, response
to solar cycles, and particularly greenhouse processes—drives a richer and more comprehensive
perspective in which Earth becomes one example.
Venus and Earth are nearly identical in size and bulk density, but Venus’s massive atmosphere
presents an extremely different system when compared with Earth’s. The upper reaches of its hot, dense
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