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Philae Lander reveals “a final mystery” from his comet tomb



Philae has been dead for many years. The last time it was sent was in July 2015; its unresponsive form is now under the rock overhang on Comet 67P/Churyumov-Gerasimenko.

However, even if the robot lander is in a cold resting state, scientists have not given up. They finally found a place where Philae bounced back on landing.

Here, it scraped a deep cut in the rubble on the comet’s surface, exposing the ice below, shining brightly with the dark rocks around it. Since comets were formed at the beginning of the solar system, this primitive ice has been hidden for 4.5 billion years.

Surprisingly, the ice is soft and fluffy. Comet 67P/CG is shaped like a rubber duck, and it is indeed a dirty snowball-this information can help us plan future comet landing missions.

Philae̵

7;s landing was shameful. Even if one of the thrusters was unusable, it was released from the Rosetta spacecraft on November 12, 2014. Then, when it hit the landing site Agilkia, its anchor harpoon did not fire, rebounded to a height of about one kilometer (0.62 miles), and then fell. Then, it touches and rebounds again. Philae finally stopped in the Abydos Valley until today.

Scientists know where the first point of contact is. After 22 months, they were able to find Philae’s final resting place. But the position of the rebound in the middle is still elusive.

Lawrence O’Rourke, an astronomer at the European Space Agency, said: “Philae has left us with the last mystery to be solved.

“It is very important to find the grounding point, because the sensor on Philae indicates that it has dug into the ground, and it is likely to expose the original ice layer hidden underneath. This will allow us to gain the valuable value of billions of years of ice.”

The team began searching for data obtained by the optical, spectral and infrared remote imaging system (OSIRIS) on the Rosetta space shuttle. They specifically look for bright patches on 67P/CG, which may indicate newly exposed ice. Considering the brightness changes on the surface of the comet, this is like looking for a needle in a haystack.

When they studied the data of the lander itself, they made a breakthrough. Or more precisely, the ROsetta magnetometer and plasma (ROMAP) instrument connected to the lander. ROMAP aims to monitor changes in the local magnetic field of comets. But when Philae crashed, the instrument’s 48 cm (19 inch) magnetometer boom bent.

This caused the boom to move relative to the lander’s body, and the team could estimate the time it took Philae to hit the ice. It also generates unique accelerometer measurements that describe Philae’s actions.

ROMAP data is correlated with data from the RCP magnetometer on Rosetta to track the precise location of the second bounce. In the end it was only 30 meters (98 feet) from the overhang.

The important thing is that the team can finally rebuild the way to rebound.

It turns out that Philae spent a full two minutes crashing near the bounce point and contacted the comet at least four times. At one point, it took about three seconds to sink 25 cm (10 inches) into the comet. Researchers say that for low-gravity environments such as 67P/CG, such a long duration is not uncommon. All these clumsy scrolling gave the site a new name.

O’Rourke said: “When viewed from above, the shape of the boulder hit by Philae reminded me of a skull, so I decided to call this area “the crest of the skull” and continue to use this subject as other features observed. “

“The right’eye’ of the’skeleton face’ is formed by the top surface of Philae compressing dust, and the gap between the boulders is the’skeleton roof gap’, Philae passes between them like a windmill.”

Skull comet(ESI / Rosetta / MPS, for OSIRIS team MPS / UPD / LAM / IAA / SSO / INTA / UPM / DASP / IDA; O’Rourke et al., 2020)

When the research team looked at the images taken by Rosetta a few months after landing, they found a 3.5-square-meter (37-square-foot) piece of bare ice, brightly reflecting the hot sunlight, where Philae scratched the comet. It is not visible in the image taken during landing because the area is in shadow.

Studying the sequence of events when the lander bounces—contact, duration, and how deep Philae sinks into the 67P/CG surface—finally provides a new and unexpected tool for describing the density of comets.

“Farae’s simple act of stamping on the side of the gap led us to conclude that this ancient, billion-year-old mixture of ice-cold dust is very soft-more than the foam or foam found on cappuccino coffee The foam is more fluffy. Bubble bath or above the waves on the beach,” O’Rourke said.

The data can also estimate the porosity of the comet. The researchers found that approximately 75% of 67P/CG is empty space, consistent with previous analysis. This is equivalent to pumice. Researchers say that the rocks on the comet may be more like Styrofoam, rather than bulky-looking boulders.

This is an interesting discovery. This solid space rock (and ice) has lingered around the solar system for 4.5 billion years, and has survived almost none.

Astronomer Jean-Baptiste Vincent of the German DLR Planetary Research Institute explained: “The mechanical tension that holds the comet ice in this dust together is only 12 Pascals.” It’s nothing but nothing.”

This may be very useful information when designing comet detectors in the future.

The team’s research results have been published in nature.


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