Posted on behalf of Adam Mann
When researchers want to know how old a particular lava flow is on Mars, they count the number of craters that pockmark the feature. Older surfaces have more craters than fresh ones. But this technique only allows scientists to estimate the relative age of one part of Mars to another.
New data may now help researchers create a crater clock that can help them pin down the absolute ages of features. Ingrid Daubar of the University of Arizona in Tucson and her colleagues are doing this by measuring how quickly craters are appearing on Mars today. By comparing images of the Martian surface taken at different times, the researchers found 201 craters that were created in the last ten years. She presented the group’s latest results at the Lunar and Planetary Science Conference in The Woodlands, Texas, on 8 March.
The team estimates that impacts create approximately 94 new craters each year that are at least several metres in size. The information is an important step in “allowing us to extrapolate this back in time and get dates that mean something on Martian surfaces,” says Jay Melosh, a geophysicist from Purdue University in West Lafayette, Indiana, who was not associated with the work.
The team has used similar techniques to come up with cratering rates for the Moon, which appears to accumulate at least 800 metre-sized impacts per year. Daubar stresses, though, that this number is based on only a handful of observations. Still, knowing the relative rate of crater formation on the Moon and Mars is significant, she says.
Image of craters on Mars: HiRISE/NASA