Space Topics: Phoenix
Mission Objectives
Study the history of water by examining water ice from below the
Martian surface.
To dig downward into a soil is to dig into the past. Phoenix's digging
arm may be able to reach as far as half a meter below the arctic surface. The
lander's instruments will be brought to bear on pristine samples from a variety
of depths within the soil, providing clues to the recent history of water
at Mars' north pole. The science team will seek to understand how the
water got there -- from below? above? as a solid, liquid, or gas? -- and how
the subsurface ice communicates chemically with the atmosphere.
Determine if the Martian arctic soil could support life.
Although Mars' surface is sterilized by solar radiation and a corrosive
chemical environment, conditions are likely very different underground. Also,
Mars' climate varies greatly over a time scale of 100,000 years due to periodic
changes in the shape of Mars' orbit and the direction and degree of its
polar tilt. Conditions near the poles could actually become favorable
for supporting life during brief periods. Life forms on Earth called
extremophiles have been found that could survive long freezes and become
reactivated when conditions are favorable. Phoenix will explore the
habitability of Mars' underground environment by testing for organic compounds
and searching for physical, mineralogical, and chemical evidence that the
subsurface ice periodically melts (even if it only melts into a very thin
layer, barely wetting individual mineral grains).
Phoenix is not actually looking for life. According to Principal
Investigator Peter Smith: "It is unlikely that a single trench in the
vast northern plains will find evidence for biological communities even if
they exist there. Our goal is to determine whether conditions favor
their preservation." There are no instruments on the spacecraft
that are designed to detect life.
Frost at the Viking 2 lander site
Credit: NASA / JPL / R. Nunes
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Study the climate and weather of the northern polar region throughout
the summer season.
The interaction between Mars' atmosphere and the soil has been studied for
a long time but is still poorly understood. At the poles, the extremes
of Mars' climate variation cause a sizeable fraction of the atmosphere to condense
and freeze every winter and sublimate again in the summer. Phoenix will
be able to track the changes in the temperature, pressure, composition, and
other factors in the atmosphere over time to provide some ground truth for mathematical
models of these complicated processes.
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