Mission Overview
Overview
Mars is a cold desert planet with no liquid water on its surface. But in the Martian arctic, water ice lurks just below ground level. Discoveries made by the Mars Odyssey Orbiter in 2002 show large amounts of subsurface water ice in the northern arctic plain. The Phoenix lander targets this circumpolar region using a robotic arm to dig through the protective top soil layer to the water ice below and ultimately, to bring both soil and water ice to the lander platform for sophisticated scientific analysis.
Image right: This map centered on the north pole of Mars is based on gamma rays from the element hydrogen -- mainly in the form of water ice. Regions of high ice content are shown in violet and blue and those low in ice content are shown in red. The very ice-rich region at the north pole is due to a permanent polar cap of water ice on the surface. Elsewhere in this region, the ice is buried under several to a few tens of centimeters of dry soil. Image Credit: NASA/JPL/UA
The complement of the Phoenix spacecraft and its scientific instruments are ideally suited to uncover clues to the geologic history and biological potential of the Martian arctic. Phoenix will be the first mission to return data from either polar region providing an important contribution to the overall Mars science strategy "Follow the Water" and will be instrumental in achieving the four science goals of NASA's long-term Mars Exploration Program.
--Determine whether Life ever arose on Mars
--Characterize the Climate of Mars
--Characterize the Geology of Mars
--Prepare for Human Exploration
The Phoenix Mission has two bold objectives to support these goals, which are to (1) study the history of water in the Martian arctic and (2) search for evidence of a habitable zone and assess the biological potential of the ice-soil boundary.
Objectives
Objective 1: Study the History of Water in All its Phases
Currently, water on Mars' surface and atmosphere exists in two states: gas and solid. At the poles, the interaction between the solid water ice at and just below the surface and the gaseous water vapor in the atmosphere is believed to be critical to the weather and climate of Mars. Phoenix will be the first mission to collect meteorological data in the Martian arctic needed by scientists to accurately model Mars' past climate and predict future weather processes.
Liquid water does not currently exist on the surface of Mars, but evidence from Mars Global Surveyor, Odyssey and Exploration Rover missions suggest that water once flowed in canyons and persisted in shallow lakes billions of years ago. However, Phoenix will probe the history of liquid water that may have existed in the arctic as recently as 100,000 years ago. Scientists will better understand the history of the Martian arctic after analyzing the chemistry and mineralogy of the soil and ice using robust instruments.
Image right: Three-dimensional image of the Martian arctic created using data from the Mars Orbiter Laser Altimeter (MOLA) aboard Global Surveyor. Image credit: NASA Objective 2: Search for Evidence of Habitable Zone and Assess the Biological Potential of the Ice-Soil Boundary
Recent discoveries have shown that life can exist in the most extreme conditions. Indeed, it is possible that bacterial spores can lie dormant in bitterly cold, dry, and airless conditions for millions of years and become activated once conditions become favorable. Such dormant microbial colonies may exist in the Martian arctic, where due to the periodic wobbling of the planet, liquid water may exist for brief periods about every 100,000 years making the soil environment habitable.
Phoenix will assess the habitability of the Martian northern environment by using sophisticated chemical experiments to assess the soil's composition of life-giving elements such as carbon, nitrogen, phosphorus, and hydrogen. Identified by chemical analysis, Phoenix will also look at reduction-oxidation (redox) molecular pairs that may determine whether the potential chemical energy of the soil can sustain life, as well as other soil properties critical to determine habitability such as pH and saltiness.
Despite having the proper ingredients to sustain life, the Martian soil may also contain hazards that prevent biological growth, such as powerful oxidants that break apart organic molecules. Powerful oxidants that can break apart organic molecules are expected in dry environments bathed in UV light, such as the surface of Mars. But a few inches below the surface, the soil could protect organisms from the harmful solar radiation. Phoenix will dig deep enough into the soil to analyze the soil environment potentially protected from UV looking for organic signatures and potential habitability.
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