Mars Trembles Quakes on Mars, but not all of them It is caused by phenomena occurring below the surface. meteorite strike.
Meteorites fall on Mars every day. Analyzing data from NASA’s InSight spacecraft, an international team of researchers found that the spacecraft’s seismometer, SEIS, had detected six earthquakes near Mars. These earthquakes were associated with the same acoustic atmospheric signals that meteorites produce as they hurtle through the Martian atmosphere. Upon further investigation, they discovered that all six earthquakes were an entirely new type of earthquake called VF (very high frequency) earthquakes.
Impacts that create VF Marsquakes occur in a fraction of a second, much shorter than the few seconds it takes for tectonic forces to create earthquakes of a similar magnitude. This is an important piece of seismic data that helps us understand the occurrence of earthquakes caused by meteorite impacts on Mars. It is also the first time that seismic data has been used to determine the frequency of impact crater formation.
“Although we cannot completely rule out a non-impact origin for each VF event, our results indicate that the entire VF class is likely caused by meteorite impacts,” the researchers wrote in their paper. study It was recently published in Nature.
Crustal Movement
Scientists have typically determined rough estimates of the meteorite impact rate on Mars by comparing the frequency of craters on the Martian surface with the expected impact rate calculated from the number of craters left by meteorites on the Moon. The lunar cratering rate models have then been adjusted to fit the Martian conditions.
Mars is particularly prone to meteorite bombardment, making the Moon a less than ideal comparison point: Not only is the Red Planet more massive and has greater gravity, it also sits closer to the asteroid belt.
Another problem is that lunar craters are often better preserved than their Martian counterparts. Not present in the solar system The Moon is dustier than Mars. Craters are often partially obscured by dust in orbital images, making them difficult to identify. Dust storms can complicate matters by covering craters with even more dust and debris (which cannot happen on the Moon, as there is no wind).
After landing, InSight will deploy the SEIS instrument. Elysium Plain In addition to detecting Martian tectonic movements, seismometers could potentially determine impact rates from earthquake data. When a meteorite strikes Mars, it creates seismic waves, just like tectonic Marsquakes, that can be detected by seismometers as they pass through the mantle and crust. The giant earthquake detected by SEIS was associated with a 150-meter (492-foot) wide crater. SEIS has since detected five more Marsquakes, all associated with acoustic signals (detected by another sensor on InSight) that are a telltale sign of a meteorite impact.
Major impact
The six impact Marsquakes detected in the seismic data were also notable for something else: the meteorite’s speed (over 3,000 meters or 9,842 feet per second) caused these events to occur faster than other types of Marsquakes, even faster than High Frequency (HF) class earthquakes. This earned them their own classification as Very High Frequency (VF) earthquakes. The InSight team used the Mars RO Orbiter’s (MRO) Context Camera (CTX) to photograph the locations of the events captured by SEIS, and the images showed new craters.
There are other seismic events that have not yet been pinpointed in craters – they are thought to be small craters formed by meteorites the size of basketballs, which would be extremely difficult to see in MRO’s orbital images.
Using the SEIS data, the researchers were able to estimate the crater’s diameter based on its distance from InSight (based on the time it took for seismic waves to reach the spacecraft) and the associated size of the VF Marsquakes. They were also able to derive the frequency of the earthquakes captured by SEIS. Applying the frequency estimate based on the data to the entire Martian surface, they estimated that approximately 280-360 VF quakes occur each year.
“The unique VF-class Marsquakes are likely consistent with an impact event,” they said in the same paper. study“It is therefore worth considering the implications of attributing all VF events to meteorite impacts.”
Their detection adds to the estimated number of impact craters on Mars, as many were previously invisible from space. What do VF impacts tell us? The rate of impact on a planet or moon is important for determining the age of that object’s surface. Using impacts, we have found that while the surface of Venus is constantly renewed by volcanic activity, most of the surface of Mars has not been covered by lava for billions of years.
Understanding the frequency of meteorite impacts could help protect spacecraft and, in the future, astronauts on Mars from potential danger. The study suggests that there are periods of higher and lower impact frequency, which may allow us to predict when meteorites are more likely to fall into the sky and when they are not. Meteorites are not as dangerous for Earth because many of them burn up in the atmosphere. The Martian atmosphere is much thinner, allowing more meteorites to get through and there is no umbrella to block meteor showers.
Nature Astronomy, 2024. DOI: 10.1038/s41550-024-02301-z
