New observations show that if life exists on Mars, it's probably going to be much deeper underground than expected
Scientists have posited that if life exists on Mars presently, it is probably hidden out of view in aquifers beneath the planet's barren surface. Unfortunately, new data collected by NASA's Mars Reconnaissance Orbiter suggests that these aquifers, if they exist, are probably much deeper inside the small ruddy planet than researchers had hoped.
Using the orbiter's SHARAD (Shallow Radar) instrument, scientists have been able to get a very detailed picture of Mars' nothern global icecap and the planet's crust below. Though the data has proven very useful in fleshing out the life cycle of the giant ice cap, it also shows that the martian lithosphere, or the outer crust, is very stiff.
Earth's lithosphere, in contrast, is somewhat soft. A large buildup of ice on Earth in a situation similar to Mars' would actually cause the crust to sag beneath its weight. On Mars, this is not happening. Scientists believe this shows that Mars' lithosphere is quite thick and cold.
Warmed internally by pressure and/or an active core, a planet's lithosphere gradually grows colder towards the outside. Mars' lithosphere being stiff enough to not sag under the immense weight of its icecaps indicates that the any warmth generated internally does not venture far from the core, making the outer crust much colder than anticipated. This cold would prevent liquid water from forming anywhere near the surface. Instead, should it exist, it would be much deeper and most likely inaccessible by any easy means.
The Mars Reconnaissance Orbiter's detailed imaging of the icecap did show evidence for a planetary climate, however. Alternating layers of dusty ice and nearly pure ice are thought to show a timetable of approximately one million year intervals. This coincides with the estimate that the cap itself is roughly four million years old. The climate changes are likely caused by variations in the planet's rotational axis and orbit.
More surface data from the northern polar region should be available very soon as NASA's Phoenix Mars Lander is slated to set down on the planet's surface in just over a week. The lander will explore the polar region and look for signs of the existence of water on the surface in the past.
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