Here at SkyFeed, I've talked about the science of earthquakes - how the shifting, sliding, pulling, and pushing of Earth's tectonic plates causes the seismic activity that we all know and love (and kind of fear). But what about our celestial neighbors? Are there earthquakes on worlds that are not Earth?
Well, in the 1970s, Apollo astronauts placed seismometers on the Moon to see what it was up to. It was switched off in 1977, but these instruments recorded more than 12,000 seismic events of varying degrees, including one quake with a magnitude of 5.5. Meanwhile, Mars has been found to have a system of faults or fissures in the crust, and possibly volcanic activity.
But moonquakes and marsquakes are different than earthquakes.
What makes moonquakes so interesting isn't so much their magnitude, but their persistence. Most quakes on Earth tend to dissipate after a minute or so because of interference with water below the surface. The surface sort of acts like a sponge to tamp down the vibrations - but not so on the Moon, which is cooler, more rigid, and obviously drier.
Its surface isn't pieced together from tectonic plates like Earth. Instead, it's been described as being like a tuning fork.
Those old Apollo instruments have recorded shallow moonquakes lasting more than ten minutes!
Some of these are likely vibrations caused by meteorite impacts, while others are probably thermal quakes caused by the difference in temperature between the lunar day and night. When sunlight first strikes the Moon's surface, the melting of the Moon's icy, frozen crust can cause it to expand, creating seismic activity.
While the most common moonquakes appear to be related to the tidal stresses between the Earth and the Moon, the mechanisms behind them aren't really well understood. But these quakes happen pretty regularly, are low magnitude, and occur at great depths below the lunar surface.
Then, there's a whole category of shallow moonquakes that originate closer the surface that still have scientists baffled.
Yes, we are still analyzing data from 1977, trying to figure out the origin of all the moon's quakes.
Scientists know even less about marsquakes, in large part because we don't have the trove of data that we do from the Moon. In fact, only the Viking landers - which touched down on Mars in the mid-1970s - had seismometers onboard, and the only quakes they detected came from vibrations as the spacecraft landed.
However, there are photographs by NASA's Mars Reconnaissance Orbiter which have revealed intriguing evidence of marsquakes and volcanic activity. The orbiter revealed a pair of long gashes in the Martian surface that appear to have formed following eruptions of a giant volcano.
So, there’s definitely something going on there. And hopefully, when the incredible launch of InSight (I watched it in person - read about it here!) reaches Mars soil sometime this Fall, it will use its technology to finally provide us with the information regarding marsquakes that we have been waiting for so long.
Hey Los Angeles, Tokyo, and Mexico City - I guess it's good to know we're not alone.
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Sources: This story was originally published on SciShow Space. I am republishing a lightly edited version on SkyFeed in light of interest in the subject. Reimers, Reid. "Moonquakes and Marsquakes." SciShow Space. YouTube. 22 July 2014. Web video.
Citation: Rovira, Lia N. "Moonquakes and Marsquakes." SkyFeed. 9 May 2018. Web article.