[meteorite-list] Mars Takes a Fresh Pounding

[Ron Baalke]

http://www.space.com/scienceastronomy/061211_st_mars_craters.html

Mars Takes a Fresh Pounding
By Tariq Malik 
space.com
12 December 2006

The planet Mars is a glutton for punishment.

Scientists have found no less than 20 new craters etched into the red
planet's surface from space rocks that pummeled Mars within the last
seven years [image
<http://www.space.com/php/multimedia/imagedisplay/img_display.php?pic=061206_mgs_newcrater_02.jpg&cap=One+of+20+new+craters+that+formed+within+the+last+seven+years+on+Mars.+Credit%3A+NASA%2FJPL%2FMSSS.+Click+to+enlarge.+>].

"If you were to live on Mars for about 20 years, you would live close
enough to one of these events to hear it," said researchers Michael
Malin, who led the study. "So there'd be a big boom and you'd know there
was an impact crater."

Malin, chief scientist at San Diego, California's Malin Space Science
Systems, and his team used the Mars Orbiter Camera aboard NASA's now
silent Mars Global Surveyor (MGS) to photograph about 30 percent of 
the planet between January and May this year. They compared the new 
images with photographs taken by MGS during earlier surveys to find 
new impact sites.

In the same study, researchers found evidence that liquid water may 
have flowed out of martian gullies within the last five to seven years 
[images
<http://www.space.com/php/multimedia/imagedisplay/img_display.php?pic=061206_mars_gullies_02.jpg&cap=The+floor+and+banks+of+a+gully+on+the+northwest+wall+of+a+crater+in+Terra+Sirenium+changed+between+December+2001+and+April+2005+due+to+a+distinct+light-toned+material+that+flowed+down+the+slope+and+formed+a+deposit+%28top%29.+The+same+change+occurred+in+a+crater+in+the+Centauri+Montes+region+%28bottom%29.+Credit%3A+Science.+Click+to+enlarge.>].

"It was just amazing that we could even do that," said Kenneth Edgett, a
Malin Space Science Systems researcher who spotted the first of the new
craters, told SPACE.com. "And it was really a whirlwind from that first
one all the through the 20th."

Malin said that it was by chance Edgett spotted an image with a new
crater and recalled a similar view taken years earlier by the MGS
orbiter. Their subsequent survey found the new craters, which range in
diameter from seven feet (two meters) to 486 feet (148 meters), and an
average impact rate of about 12 per year.

A few months after Malin and his team performed their survey, the MGS
probe went silent and is thought to be lost after 10 years of 
spaceflight.

The research is detailed in the most recent issue of the journal
Science, and it validated crater impact models of Mars that until now
were based solely on theory, Malin said.

The new craters also suggest a potential hazard for future astronaut
explorers on long-duration missions to the red planet, he added.

"There is a hazard, it's probably a low hazard," Malin said. "But it's
one we need to think about in terms of these objects hitting Mars at a
fairly substantial rate."