Science.-Philae lander outlined a skull on Comet 67P / CG

MADRID, 28 (EUROPA PRESS)

After years of work, the second landing site for the Philae lander has been identified by ESA at a location on Comet 67P / CG that the spacecraft outlined in the shape of a skull.

Philae, the lander of the Rosetta mission, has left its mark on billion-year-old ice, revealing that the comet’s icy interior is softer than the foam of a cappuccino.

Philae descended to the comet’s surface on 12 November 2014. He recovered from his initial landing site in the area called Agilkia and embarked on a two-hour flight, during which he collided with the edge of a cliff. and fell towards a second landing site. Philae eventually stopped in Abydos, in a protected location that was only identified in the Rosetta footage 22 months later, just weeks before the Rosetta mission ended.

ESA’s Laurence O’Rourke, who played the lead role in Philae’s search in the first place, was also determined to locate the previously unknown second landing site.

“Philae left us one last mystery waiting to be solved,” O’Rourke said in a statement. “It was important to find the landing site because sensors at Philae indicated that it had been dug into the surface, most likely exposing the primitive ice hidden underneath, giving us priceless access to billions of years of ice.”

Together with a team of mission scientists and engineers, he began collecting data from the Rosetta and Philae instruments to find and confirm the “lost” landing site.

Although a bright patch of “sliced ​​ice” seen in the high-resolution images from Rosetta’s OSIRIS camera was crucial in confirming the position, it was the boom of Philae’s ROMAP magnetometer that proved to be the star of the show. The instrument was designed to take measurements of the magnetic field in the comet’s local environment, but for the new analysis, the team looked at the changes recorded in the data that emerged when the boom, which protrudes 48 centimeters from the lander, was physically moves when it hits a surface. This created a characteristic set of spikes in the magnetic data as the arm moved relative to the lander’s body, providing an estimate of the duration of Philae’s stomp on the ice. The data could also be used to limit Philae’s acceleration during these contacts.

The ROMAP data were cross-correlated with that collected by the Rosetta RPC magnetometer at the same time to determine Philae’s attitude and rule out any background magnetic field influence from the plasma environment around the comet.

A new analysis of the landing data found that Philae had spent nearly two full minutes at the second landing site, making at least four different surface contacts during her passage. A particularly noticeable footprint revealed in the images was created when Philae’s upper surface is dipped 25 centimeters into ice on the side of a crevasse, leaving identifiable marks on its derrick and sides. The spikes in the magnetic field data from the arm movement showed that it took Philae three seconds to create this particular depression.

“The shape of the rocks Philae hit reminded me of a skull when viewed from above, so I decided to call the region ‘ridge on top of the skull’ and continue on that topic for other observed features,” says O ‘Rourke.

“The right” eye “of the” skull face “was formed by the upper surface of Philae compressing the dust, while the space between the rocks is a” crack in the upper part of the skull “, where Philae served as a windmill for pass between them.

Analysis of the images and data from OSIRIS and Rosetta’s VIRTIS spectrometer confirmed that the light exposure was ice water covering an area of ​​approximately 3.5 square meters. Although the ice was mostly in shadow upon landing, the Sun was directly illuminating the area when the images were taken months later, illuminating it like a beacon to stand out against everything around it. The ice was brighter than its surroundings because it had not previously been exposed to the space environment and subjected to space weather.

“It was a light that shone in the dark,” says Laurence, noting that she was only 30 meters away from where the image of Philae was finally captured on the comet’s surface.

The study also provides the first in situ measurement of the smoothness of frozen dust within a comet rock.

“The simple action of Philae stamping on the side of the slit allowed us to discover that this ancient, billion-year-old iced powder blend is extraordinarily soft, softer than the froth of a cappuccino, or the foam found in a bubble bath or on top of the waves by the sea, “adds O’Rourke.