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NASA sent its InSight lander to Mars with an ambitious mission: to study the deep internal structure of the planet. A crucial part of that effort – the “mole” – failed despite two years of trying to save it.
The Mole is a revolutionary thermal probe designed to dig 16 feet into Martian soil and take the temperature of the planet. Its measurements have reportedly revealed clues as to how the planet formed and changed over the 4.6 billion years – a story that would help scientists track down Martian water and possibly life.
But the mole made little headway in the surprisingly thick soil. Now, the InSight team must ration the solar power from the lander. NASA announced Thursday that the mole will not be able to dig its hole.
“It’s kind of a personal tragedy,” Sue Smrekar, a senior scientist on the InSight team who spent 10 years working on the mole, told Insider. “Everyone went out of their way to make this work. So I can’t ask for anything more.”
No other planned NASA mission to Mars can take the internal temperature measurements the mole was designed for.
“This was our best attempt to get this data,” added Smrekar. “From my personal point of view, it’s super disappointing, and scientifically it’s a very big loss as well. So it really sounds like a huge disappointment.”
An unexpected energy crisis
The InSight team spent two years maneuvering the lander’s robotic arm to see if it could help the mole dig more. The probe, a 16-inch-long pile pilot, is designed to exploit loose dirt that other missions to Mars have encountered. The soil would sink around the outer shell of the mole and provide friction to keep hammering deeper.
But in February 2019, the mole found itself bouncing off a firm ground foundation called ‘duracrust’. The next two years were spent troubleshooting, sending new software to InSight to teach its robotic arm new maneuvers to help the mole, and anxiously awaiting photos that might show progress.
“It has just been a huge effort across the board, and we never expected,” Smrekar said. “We thought we were going to drill the hole.”
The InSight team first had the robotic arm push on the mole, but that just got it out of the hole. Once they put the probe back into the ground, a year later, they had the arm stack the dirt on top of it, hoping that this would provide enough friction for the probe to dig deeper.
But the mole made no progress with 500 hammer blows last Saturday. The top was only 2 or 3 centimeters below the surface.
By this time, InSight’s problems were getting worse. Unlike other sites where NASA sent rovers and landers, the open plain where InSight is located did not have strong gusts of wind. Smrekar calls such bursts “cleanup events” because they blow the ubiquitous red dust of the planet on all the robots in the region. Without them, InSight’s solar panels have accumulated a large layer of dust.
At the same time, the seasons were changing and InSight’s home on a flat plain near the equator of Mars was getting cooler. In the cold, InSight will need more power to stay functional, even though its solar panels absorb less sunlight than they should.
“The power is going down and so we come to a period where, for probably two or three months, we’re probably going to have to stop doing instrument operations for a while and sort of go into survival mode warms up on Mars,” Smrekar said.
With this new time constraint, Saturday’s pounding attempt was the mole’s last chance to burrow.
Over the next two years, InSight will stay tuned for earthquakes on Mars and collect data on the rumbling of the planet with its seismometer. It can give a glimpse of the interior of the planet. Already, earthquakes on Mars have revealed that the Martian crust is drier and more fragmented than scientists had thought – more like the moon than the Earth.
The internal temperature of a planet reveals its history
If the mole had struck up to 16 feet lower, it would have measured temperatures all along its hole. This would allow scientists to calculate how much heat is leaving Mars – a metric called “heat flux.”
“It’s a single number, the heat flow, but it has ramifications for all kinds of aspects of understanding Mars,” Smrekar said.
Part of the heat leaving a planet is waste heat from its formation, but it also comes from decaying radioactive elements. Measuring heat flux would tell scientists how much radioactive material is inside the Martian crust – the planet’s outer layer – compared to the mantle below.
This would reveal not only how matter was distributed when the planet was formed (and whether it is made of the same matter as Earth), but also how the internal structure of the planet has changed over time.
“It goes back to understanding the early evolution of Mars, that time when there was a lot of liquid water on the surface,” Smrekar said.
A higher concentration of radioactive material in the mantle would make this layer more active. More radioactive material in the crust could keep the top layers of the planet warm.
The heat flow could also indicate how deep it would be necessary to drill into Mars to reach liquid water today. The earth’s groundwater may still harbor microbial life. Future humans who travel to Mars will likely need to collect water there.
It is now impossible to measure the heat flux of the planet in the foreseeable future.
“I was hoping to get the data and be able to figure out what this means for Mars,” Smrekar said.
Read the original article on Business Insider
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