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The NASA landing Perseverance Mars rover next month there will be some serious waves, some of which could help scientists better understand the structure of the red planet.
Perseverance, the centerpiece of NASA’s $ 2.7 billion Mars 2020 life-hunting and sample-caching mission, is set to land inside the 45 km-wide Jezero Crater on February 18. one of the rover’s cousins, NASA InSight Mars lander, will attempt to detect more than 2,000 miles (3,200 kilometers) away, according to a new study.
If that happens, it will first be a space flight: No spacecraft has ever “heard” such a landing on another planet in this manner, members of the InSight team said.
In photos: NASA’s Mars Perseverance rover mission to the Red Planet
InSight’s super-sensitive seismometer suite resumed hundreds of earthquakes since the lander landed in November 2018 in a Martian plain known as Elysium Planitia. Members of the InSight team are using these measurements to map the interior of the Red Planet in unprecedented detail, the primary objective of the mission.
However, such interpretive work can be tricky.
“Unlike on Earth, where you can independently determine when and where [seismic] the source occurred, and of course its size, on March, we have only one station, and we both try to identify the source mechanisms and the structure of the planet through which the waves propagated, ”says Ben Fernando, lead author of the study and member of the InSight team, a Ph.D. student at the University of Oxford in England, told Space.com.
“To separate these two elements from each other is not necessarily trivial,” he added. “In the simplest explanation, if you were in a room and couldn’t see, it’s hard to tell if someone is talking very far away or quietly near you. And on top of that, if you don’t. didn’t know what shape the coin was, that would be even more difficult. “
The Perseverance landing therefore represents a great opportunity for InSight scientists – a chance to collect impact-generated seismic data, the details of which are known in advance, Fernando and colleagues wrote in the new study.
A decent chance
March 2020 will use the same entry, descent, and landing (EDL) strategy as its predecessor, the Curiosity Mars rover, safely taken down in August 2012.
March 2020 will hit the thin Martian atmosphere hard, be considerably slowed down by friction and then deploy a supersonic parachute to decelerate further. About seven minutes after atmospheric entry, a rocket propelled sky crane will lower Jezero’s Ground Perseverance gently on cables, then fly off to intentionally crash from a safe distance.
This last step will not generate seismic waves of appreciable strength. But two other points in the EDL sequence are likely to produce relatively strong signals, according to Fernando and his team.
One of these signals will be generated by a sonic boom, which will occur after March 2020 is about 60 miles (100 km) from the Martian surface, an altitude at which the atmosphere is dense enough “for substantial compression. to happen, ”the researchers said. written in the new study.
Some of the energy from this boom – which will die out when the spacecraft goes subsonic, approximately three minutes before touchdown – will reach the Martian surface and be converted into seismic waves. But that signal won’t be strong enough to be picked up by InSight, which is about 2,145 miles (3,452 km) from the Perseverance landing site, calculated Fernando and his team, citing the dissipating effect of Martian winds as a factor. key.
The other signal will come via an actual surface impact – twin impacts, in fact. Shortly after March 2020 reaches the atmosphere, the spacecraft will eject two “Cruise Mass Balance Devices” (CMBD) to change its center of mass. The CMBDs, each of which weighs 170 pounds. (77 kilograms), will drop from a great height, at an altitude of about 900 miles (1,450 km), and strike the ground at an estimated speed of 8,700 mph (14,000 km / h), Fernando said.
Mars InSight in photos: NASA mission to probe the Martian core
It is not known how strong the seismic waves will be from the impacts of the CMBD; InSight has yet to detect any confirmed impact on Mars, so forecasting is difficult. But Fernando and his team generated estimates based on data collected here on Earth and on the moon, and these numbers suggest that InSight has a decent chance of measuring waves.
“In a realistic best case (and assuming the same meteorological and sound spectra as from the same period a Martian year earlier), the required signal-to-noise ratio would be sufficient for positive detection 40% of the time,” wrote Researchers. in the new study, which has been submitted (but not yet accepted) to the journal Earth and Space Sciences. You can read a free pre-print here.
There is luck in that relatively rosy figure: Waves generated by the CMBD will arrive at InSight’s location in the early evening, Elysium Planitia time, the quieter part of the day, Fernando said.
Detection would be a big deal for members of the InSight team. They would know precisely how far and how fast the seismic waves have traveled.
“If you know how fast they went, you can start to determine what were the structures through which they spread,” Fernando said.
Perseverance will also aim to document its own landing in an unprecedented way, by the way. March 2020 features two microphones, one of which will attempt to capturing the dramatic sounds of EDL on February 18. (The other is part of Perseverance’s rock-zapping SuperCam system.) No Mars spacecraft has ever managed to record the raw sounds of the Red Planet before.
Other landings?
Perseverance isn’t the only spacecraft to land on Mars this year. From China Tianwen-1 mission will arrive in orbit on February 10 and drop a lander and rover on the Red Planet about two months later, if all goes according to plan.
The InSight team would love to listen to the Tianwen-1 landing, Fernando said. But details about the mission – in particular, its exact time and landing location – are hard to come by, so “making predictions about the detectability of this signal is not possible” at this time, the researchers wrote. in the article.
The European-Russian ExoMars program is launching a lander-rover duo on Mars in 2022. InSight will almost certainly not be able to detect the seismic signals from this landing sequence, given that the ExoMars duo will land on the other side of the planet from InSight, Fernando said.
SpaceX intends to start flying its next-gen Starship spacecraft to Mars soon – maybe as early as 2024, said Elon Musk, founder and CEO of the company. If InSight lives long enough, it might be able to document the touchdown of one or more of these 165-foot-tall (50-meter) stainless steel spacecraft.
“It’s not out of the question,” Fernando said. “It just depends on where they decide to land.”
Mike Wall is the author of “Over there“(Grand Central Publishing, 2018; illustrated by Karl Tate), a book on the search for extraterrestrial life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook.
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