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tem provides information about how quickly or slowly surface features cool off after sunset, which
gives an indication of where the surface is rocky and where it is dusty. Odyssey's observations
have helped evaluate potential landing sites for the Mars Exploration Rovers. When the rovers
reach Mars, radio relay via Odyssey will be one way they will return data to Earth.
! Mars Reconnaissance Orbiter (2005): This mission is being developed to provide detailed
information about thousands of sites on Mars, connecting the big-picture perspective of an orbiter
with a level of local detail that has previously come only from landing a spacecraft on the surface.
The spacecraft's telescopic camera will reveal martian landscapes in resolution fine enough to
show rocks the size of a desk. Maps of surface minerals will be produced in unprecedented detail
for thousands of potential future landing sites. Scientists will search in particular for types of miner-
als that form in wet environments. A radar instrument on the orbiter will probe hundreds of meters
(or yards) below Mars' surface for layers of frozen or melted water, and other types of geologic lay-
ers. Another instrument will document atmospheric processes changing with Mars' seasons, and
study how water vapor enters, moves within and leaves the atmosphere.
! Mars Scouts (2007 and later): Mars Scouts are competitively proposed missions intended to
supplement and complement, at relatively low cost, the core missions of NASA's Mars Exploration
Program. From 25 original proposals, NASA selected four candidate Scout missions in late 2002
for further study. One will be chosen in August 2003 as the first Mars Scout, for launch in 2007.
The four finalists include an orbiter, a lander, an airplane, and a quick dip into Mars' atmosphere to
fetch dust and gas samples back to Earth. Mars Volcanic Emission and Life Scout consists of an
orbiter for exploring Mars' atmosphere for emissions that could be related to active volcanism or
microbial activity. Phoenix is a surface laboratory that proposes to land in Mars' northern plains to
investigate water ice, organic molecules and climate. The Aerial Regional-scale Environmental
Study proposes to fly a rocket-propelled aircraft through Mars' atmosphere to measure water vapor
and other gases near the surface for improved understanding of the chemical evolution of the plan-
et and potential biological activity. The Sample Collection for Investigation of Mars would swoop
close enough to the martian surface to grab a sampling of atmospheric dust and gas and return
them back to Earth. A second round of Scout solicitation in the future will select a handful of addi-
tional Mars Scout missions, one of which would fly in 2011.
! Mars Science Laboratory (2009): NASA proposes to develop and launch a roving science lab-
oratory that would operate on Mars for more than a year and travel for at least several kilometers
or miles. The mission would mark major advances in measurement capabilities and surface
access. The rover will examine the potential of the Red Planet as a habitat for extant or extinct
life. It would also demonstrate technologies for accurate landing and surface-hazard avoidance that
will be necessary for sending future missions to sites that are scientifically compelling but difficult to
reach. This mission is designed to make the transition from a program in which we "follow the
water" to one in which we "follow the clues to search for the missing carbon" -- and hence to per-
form the first indirect life detection in a generation on the martian surface.
! The Next Decade of Mars Exploration: For the second decade of this century, NASA propos-
es additional reconnaissance orbiters, rovers and landers, and the first mission to return samples
of martian rock and soil to Earth. The flexible program includes many options. Scientists and mis-
sion planners foresee technology development for advanced capabilities, such as Mars ascent
vehicle, automatic rendezvous in Mars orbit and planetary protection.
ers serve as a frozen gallery of the solar system's early days.
Thus, even if life never developed on Mars -- something that we cannot answer today
-- scientific exploration of the planet may yield critical information unobtainable by any
other means about the pre-biotic chemistry that led to life on Earth. Mars as a fossil
graveyard of the chemical conditions that fostered life on Earth is an intriguing possibil-
Science Investigations
The Mars Exploration Rover mission seeks to determine the history of climate and
rover is equipped with a suite of science instruments that will be used to read the geo-
logic record at each site, to investigate what role water played there, and to determine
how suitable the conditions would have been for life.
Science Objectives
Based on priorities of the overall Mars Exploration Program, the following science
objectives were developed for the 2003 rovers:
! Search for and characterize a diversity of rocks and soils that hold clues to
past water activity (water-bearing minerals and minerals deposited by
precipitation, evaporation, sedimentary cementation, or hydrothermal activity).
! Investigate landing sites, selected on the basis of orbital remote sensing, that
have a high probability of containing physical and/or chemical evidence of the
action of liquid water.
! Determine the spatial distribution and composition of minerals, rocks and soils
surrounding the landing sites.
! Determine the nature of local surface geologic processes from surface
morphology and chemistry.
! Calibrate and validate orbital remote-sensing data and assess the amount
and scale of heterogeneity at each landing site.
! For iron-containing minerals, identify and quantify relative amounts of specific
mineral types that contain water or hydroxyls, or are indicators of formation by
an aqueous process, such as iron-bearing carbonates.
! Characterize the mineral assemblages and textures of different types of rocks
and soils and put them in geologic context.
! Extract clues from the geologic investigation, related to the environmental
conditions when liquid water was present and assess whether those
environments were conducive for life.
Science Instruments
The package of science instruments on the rovers is collectively known as the Athena
science payload. Led by Dr. Steven Squyres, professor of astronomy at Cornell
University, Ithaca, N.Y., the Athena package was originally proposed to fly under differ-
ent Mars lander and rover mission concepts before being finalized as the science pay-
load for the Mars Exploration Rovers.
The package consists of two instruments designed to survey the landing site, as well
as three other instruments on an arm designed for closeup study of rocks. Also on the
arm is a tool that can scrape away the outer layers of rocks. Those instruments are
supplemented by magnets and calibration targets that will enable other studies.
The two instruments that will survey the general site are:
! Panoramic Camera will view the surface using two high-resolution color
stereo cameras to complement the rover's navigation cameras. Delivering
panoramas of the martian surface with unprecedented detail, the instrument's
narrow-angle optics provide angular resolution more than three times higher
than that of the Mars Pathfinder cameras. The camera's images will help
scientists decide what rocks and soils to analyze in detail, and will provide
information on surface features, the distribution and shape of nearby rocks, and
the presence of features carved by ancient waterways.
! The Mini-Thermal Emission Spectrometer is an instrument that sees
infrared radiation emitted by objects. It will determine from afar the mineral
composition of martian surface features and allow scientists to select specific
rocks and soils to investigate in detail. Observing in the infrared allows
scientists to see through dust that coats many rocks, allowing the instrument to