There are millions of impact craters all over the Solar System, but direct evidence of the massive collisions that form them is very hard to come by – and therefore very valuable. While carrying out its routine monitoring of the weather on the Red Planet, the Mars Color Imager (MARCI) on NASA’s Mars Reconnaissance Orbiter (MRO) has inadvertently snapped before and after images of the largest fresh meteor impact crater found anywhere in the Solar System.
Scientists observing data from the Mars Color Imager (MARCI) on NASA’s Mars Reconnaissance Orbiter (MRO) recently got a lucky break, however. As it carried out its routine monitoring of the weather on the Red Planet, MARCI inadvertently snapped before and after images of the largest fresh meteor impact crater found anywhere in the Solar System.
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The discovery of the crater came about during the most routine of chores. Bruce Cantor, deputy principal investigator at Malin Space Science Systems, which built and operates the MARCI, studies images and data sent back from the MRO to learn more about the Martian weather. This is done partly for scientific reasons, but also to keep an eye on any weather that might endanger the solar-powered Opportunity rover.
The advantage of taking so many weather images is that its a bit like taking a planet-wide stop-motion video of Mars and, with a bit of attention, it’s possible to catch changes that more advanced imaging surveys might miss. In this case, Cantor noticed a dark spot on an image taken near the equator about two months ago.
"It wasn't what I was looking for," Cantor says. "I was doing my usual weather monitoring and something caught my eye. It looked usual, with rays emanating from a central spot."
Cantor compared the image to earlier ones, at first selecting those taken about a month apart. It turns out that though the spot was there last year, it wasn't there five years ago. Eventually, he narrowed down the appearance of the spot to sometime between March 27, 2012 and March 28, 2012. The spot was then examined directly by the MRO’s High Resolution Imaging Science Experiment (HiRISE) and the Context Camera (CTX), and the images compared to earlier high-resolution ones taken of the area.
The images confirmed that a new impact crater measuring 159 x 143 ft (48.5 x 43.5 m), which HiRISE Principal Investigator Alfred McEwen described as unusually shallow, had appeared and that it was surrounded by a dozen smaller craters, indicating that a meteor had exploded on impact and scattered debris over the dune field. In addition, many of the slopes in a 5 mile (8 km) area showed signs of landslides.
According to McEwen, the meteor was between 10 to 18 ft (3 to 5 m) in diameter and that it was less than a third the width of the object that exploded over Chelyabinsk, Russia. The Martian meteor was able to reach the surface without burning up because of the extremely thin atmosphere.
The MRO was launched August 12, 2005 from Cape Canaveral Air Force Station, Florida and arrived in Mars orbit on March 10, 2006. Originally scheduled for a two-year mission, the unmanned probe carries a suite of instruments including high-resolution cameras, spectrometers and radar designed to study the climate of Mars with a particular emphasis on the water cycle in the Martian atmosphere and looking for water and water-formed minerals on the surface.
"Studies of fresh impact craters on Mars yield valuable information about impact rates and about subsurface material exposed by the excavations," says Leslie Tamppari, deputy project scientist for the Mars Reconnaissance Orbiter mission at NASA's Jet Propulsion Laboratory (JPL) in California. "The combination of HiRISE and CTX has found and examined many of them, and now MARCI's daily coverage has given great precision about when a significant impact occurred."
The video below outlines the discovery.