The Solar Systems Largest Impact Crater Yields Clues to Radical Changes in Mars Atmosphere

Mars-basin-1-enlarged The prehistoric Chicxulub crater left by an asteroid collision in Mexico's Yucatan Peninsula could yield clues about what Mars was like billions of years ago, according to NASA planetary geologist Adriana Ocampo, who is studying an ancient impact crater buried deep under southeastern Mexico for hints about what impact craters can reveal about planet formation. Her work could shed light on a giant crater on the surface of Mars -the largest in the Solar System- that was created by an impact from an object the size of Pluto (image left).

Astronomers have been puzzled for decades about a huge impact crater on the surface of Mars — the largest known crater in the solar system — and new evidence last month suggests it was caused by the impact of an asteroid the size of the moon.

The Mexican crater, known as Chicxulub, was created when an asteroid that smacked into Earth 65 million years ago in a catastrophe that wiped out around half the planet's species and was perhaps responsible for the dinosaurs becoming extinct.

Studying the debris spewed by the collision may answer questions about radical changes in atmosphere that can result from massive asteroid hits, Ocampo, has been studying the Yucatan crater for a decade, told Reuters.

Adriana3 "It's a natural laboratory because of its similarities to what we can find on other planets like Mars where humans can't go," Ocampo said of Mexico's smaller crater.

The crater on Mars, measuring 5,300 miles across, is so big that it has left half the planet at a lower elevation.

NASA's Mars Reconnaissance Orbiter and Mars Global Surveyor have provided detailed information about the elevations and gravity of the Red Planet's northern and southern hemispheres. A new study using this information may solve one of the biggest remaining mysteries in the solar system: Why does Mars have two strikingly different kinds of terrain in its northern and southern hemispheres? The huge crater is creating intense scientific interest.

The mystery of the two-faced nature of Mars has perplexed scientists since the first comprehensive images of the surface were beamed home by NASA spacecraft in the 1970s.

A giant northern basin that covers about 40 percent of Mars' surface, sometimes called the Borealis basin, is the remains of a colossal impact early in the solar system's formation, the new analysis suggests. At 8,500 kilometers (5,300 miles) across, it is about four times wider than the next-biggest impact basin known, the Hellas basin on southern Mars. An accompanying report calculates that the impacting object that produced the Borealis basin must have been about 2,000 kilometers (1,200 miles) across. That's larger than Pluto. It appears to have held an ocean in crater the size of the combined areas of Asia, Europe and Australia,the early days of the planet, before Mars lost so much of its atmosphere and the water either sublimated away or froze beneath the surface.

Mexico's crater is a much smaller 100 miles in diameter and is now half a mile underground, where rocks and earth have buried it over millions of years. Space geologists believe the asteroid hit in the Caribbean Sea, probably causing a huge tsunami.

Information from Chicxulub could also give clues about whether or not there was water on the surface of Mars long after the planet was dented by the massive asteroid hit.

Scientists have detected frozen water on the surface of the red planet. Martian seas could have disappeared when the planet was bombarded by smaller meteors that changed its atmosphere and dried it out, Ocampo said.

Casey Kazan.



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