Curiosity really has made an impact on Mars. A sharp-eyed orbiter has spotted craters at the site where castoffs from the NASA rover鈥檚 landing gear fell to the surface in August. Examining the damage can help reveal what it takes to scar the Red Planet.
Just after entering the Martian atmosphere, Curiosity鈥檚 descent capsule dropped two laptop-sized blocks of tungsten, each weighing about 75聽kilograms, which helped the craft tilt and glide towards its landing site in Gale crater.
The HiRISE camera on NASA鈥檚 Mars Reconnaissance Orbiter has now snapped detailed photos of the surrounding area, showing that the blocks made craters 3聽metres to 5聽metres wide. The scars are about 80聽kilometres to the west of Gale crater 鈥� too far for the rover to investigate, because it can travel only about 100聽metres per day.
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But studying the impact zone from orbit can give planetary scientists cleaner data on Mars鈥檚 surface and atmospheric properties than they could get from the hundreds of natural impact craters that they have already photographed.
鈥淲e think we kind of understand crater formation in terms of an object of a certain mass, at a certain velocity, should go ahead and create a crater of a certain size and depth,鈥� says of Northern Arizona University in Flagstaff. 鈥淏ut most of what we know is based on theory. This gives us some actual ground truth.鈥�
Scattershot asteroids
This isn鈥檛 the first time we鈥檝e studied artificial craters, says of Purdue University in West Lafayette, Indiana. Discarded landing gear from other craft sent to the moon and Mars have been studied in detail, especially since the Mars Reconnaissance Orbiter arrived in Martian orbit in 2006. But the tungsten blocks, with their simple shapes, are closer to a theoretician鈥檚 heart, he says.
鈥淭hey made craters much closer to the kind of craters that natural asteroid impacts make.鈥�
The HiRISE camera also caught other impact scars flanking the ballast craters, which probably came from Curiosity鈥檚 cruise module, the doughnut-shaped section that provided electricity and propulsion on the journey from Earth.
Mars is much closer than Earth to our solar system鈥檚 main asteroid belt, and its much thinner atmosphere provides less protection from incoming space rocks. Melosh and colleagues have been trying to figure out the numbers and strengths of asteroids that regularly break up in the Martian atmosphere, based on the patterns that their pieces leave on the ground.
Seeing the scars from broken bits of the cruise stage, the durability of which is already known, will help test his theories. 鈥淔or that reason, the debris from the ring is even more interesting,鈥� he says.
