SpaceX’s derelict rocket will crash and create a worrying new Moon crater
It’s expected to crash on March 4th
Misplaced concern
It is, however, surely more environmentally friendly for a dead rocket to end up on the Moon than being scattered through Earth’s upper atmosphere in the form of metal oxide particles, which is what happens during a re-entry burn up. The Moon also lacks an atmosphere to shield it from space debris, so it is accumulating naturally occurring impact craters all the time.
The Lunar Reconnaissance Orbiter has already imaged a 19 meter crater formed when a half a tonne lump of asteroid rock traveling about ten times faster than the Falcon 9 struck the surface in March 2013. Over the past decade, hundreds of smaller impacts, by chunks of rock weighing as little as half a kilogram, have been spotted byNasa’s lunar impact monitoring project.
The coming impact will be on the lunar far side, so we won’t be able to see it happen. But spacecraft orbiting the Moon will be able to image the impact crater afterward. Will we learn anything new? There have been several previous deliberate crashes onto the Moon, so we know what to expect.
For example, the considerably larger upper stages of rockets used in the Apollo landing missions were crashed so that vibrations detected by seismometers installed on the surface could be used to investigate the lunar interior. TheApollo seismometerswere turned off long ago, and is not clear whether the seismometer on China’sChang’e 4 far side lunar landerwill be able to provide any useful data this time.
A precisely targeted, deliberate crash was also achieved in 2009 whenNasa’s LCROSS missionsent a projectile into a permanently shadowed polar crater – making a smaller crater on its icy floor and throwing up a plume that proved to contain the hoped for water vapor.
Biological contamination
So I’m not bothered by one more crater being made on the Moon. It already has something like half a billion craters that are ten meters or more in diameter. What we should worry about is contaminating the Moon with living microbes, or molecules that could in the future be mistaken as evidence of former life on the Moon.
Most nations have signed up toplanetary protectionprotocols that seek to minimize the risk of biological contamination from Earth to another body (and also from another body back to Earth). The protocols are in place for reasons both ethical and scientific. The ethical argument is that it would not be right to put at risk any ecosystem that may exist on another body by introducing organisms from Earth that might thrive there. The scientific argument is that we want to study and understand the natural conditions on each other body, so we should not risk compromising or destroying them by wanton contamination.
The biggest recent breach of the COSPAR protocols was in 2019 when the privately funded Israeli lunar lander Beresheet crashed on the Moon, carrying DNA samples and thousands oftardigrades. Those are half millimeter long organisms that can tolerate, though not be active in, the vacuum of space. These, and presumably also the microbes that lived in their guts, are now scattered across the Beresheet crash site.
Most likely none of these will end up in a niche where there is enough water for them to revive and become active, but that is not a risk we should be taking. The DSCOVR Falcon 9 was not sterile upon launch, but nor did it carry a biological cargo. It’s also been seven years in space, so by now the risk of biocontamination is vanishingly small – but the more things we send to the Moon, the more careful we must be and the harder it will be to enforce any rules.
Read more:Swipe left-right to see before and after images of natural lunar crater
Article byDavid Rothery, Professor of Planetary Geosciences,The Open University
This article is republished fromThe Conversationunder a Creative Commons license. Read theoriginal article.
Story byThe Conversation
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