Map hints at polar shift on Mars

[Dover]

Map hints at polar shift on Mars
Scientists say impacts trace ancient equator

AGU / JGR
This map shows gravity readings for regions of Mars, reflecting surface elevation. The black dot indicates the center of a great circle of impacts and may represent the planet's ancient south pole.



Updated: 4:13 p.m. ET April 18, 2005A new look at ancient craters on Mars finds five that are arrayed along an arc that's part of a giant circle around the planet. The circle may have been Mars' equator long ago.

The craters might all have been formed when one giant asteroid broke apart, its fragments slamming into the planet at different times and locations around the then-equator, says Jafar Arkani-Hamed of McGill University in Montreal.

If the analysis is right, it has implication for where water might lurk beneath the Martian surface today.

Ancient Mars
Mars was once warmer and wetter, several lines of evidence suggest. Scientists speculate that while much of the water evaporated into space, some may have penetrated underground and remains. Water is a key ingredient for life as we know it.

Like Earth, the poles of Mars have not always been where they are today. In fact, Mars seems to have transformed dramatically during its roughly 4.5-billion-year life. One striking feature known as the Tharsis Bulge — it's 5 miles high (8 kilometers) and covers a sixth of the planet — illustrates how a changing shape would have altered its axis over time, scientists say.

The five basins identified in the new study are Argyre, Hellas, Isidis, Thaumasia and Utopia. They were thought to have all formed prior to the development of the Tharsis Bulge...cont'd

http://msnbc.msn.com/id/7547963/

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Possible Ancient Equator on Mars Revealed

http://www.space.com/scienceastronomy/050418_mars_equator.html