For future colonists on Mars, there will be all sorts of risks, such as extreme weather and temperature conditions, radiation, and the human physiological problems associated with life under reduced gravity. But another problem means that colonists on Mars have to keep a constant lookout over their heads.
While Mars and Earth are regularly hit by space debris – dust, small rocks, and larger meteorites – meteors on our planet usually evaporate in the atmosphere.
“On Mars, on the other hand, the impactors usually make it to the surface with a surface pressure of 1/100 that of Earth,” says the team of the HiRISE camera of the Mars Reconnaissance Orbiter (MRO).
A small impact crater on Mars that has formed over the past 5 years as seen by the HiRISE camera of the Mars Reconnaissance Orbiter. Photo credit: NASA / JPL / UArizona.
HiRISE (High Resolution Imaging Science Experiment) aboard MRO captured this image of a small impact crater that has formed sometime in the past 5 years. Although the crater is small, the ejection jets ejected by the impact are easy to spot and extend for nearly a kilometer.
How often does this happen on Mars? A 2013 study estimated that the Red Planet is washed by more than 200 small asteroids or comet pieces each year, forming craters at least 3.9 meters (12.8 feet) in diameter. As on Earth, even a small impact would devastate any Martian settlement. But impacts of this size on Mars are more common.
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Mars is roughly half the size of Earth in diameter, and the thinner air surrounding the planet has an atmospheric volume less than 1% of the Earth’s volume. The atmospheric composition also differs significantly: mainly based on carbon dioxide, while the earth is rich in nitrogen and oxygen.
MRO has been in orbit around Mars since 2006, and one of the benefits of having a spacecraft orbiting another planet for several years is the ability to make long-term observations and interpretations. HiRISE images have discovered numerous “fresh” craters that have formed over the years, and since multiple regions on Mars have been repeatedly imaged, scientists can examine the before-and-after images to calculate the rate of impact based on new craters .
A 2010 image of ice excavated on Mars following a recent meteorite impact. Image from the Mars Reconnaissance Orbiter’s High Resolution Imaging Science Experiment (HiRISE) camera. Photo credit: NASA / JPL-Caltech / Univ. from Arizona
The 2013 study showed that the frequency with which new craters at least 3.9 meters in diameter form on any area of the Martian surface per year is roughly the same as that of the US state of Texas.
Just one more thing that will be a challenge for anyone who dares to live on Mars.
See the original image and more details of MRO on the HiRISE website.