Before coming to rest on Comet "Tchouri" six years ago, the lander Philae bounced off the surface several times, sinking into a ice cream "as fluffy as cappuccino froth". This is the conclusion of a study published on Wednesday.
In 2014, more than ten years after its launch, the European Space Agency (ESA) Rosetta mission finally reached its destination:comet 67P / Churyumov – Gerasimenko – or comet "Tchouri". The object was then more than 500 million kilometers away of the earth. One of the main objectives of the mission was to land a small lander named Philae on the surface of the object. On November 13 of that year, it then became the first human artifact to attempt a soft landing on a comet.
Unfortunately, the landing did not go as planned. Poor Philae indeed bounced on the surface before coming to rest in a position that did not allow it to receive enough sunlight (and therefore energy). Eventually, ESA officially gave up trying to communicate with its lander, which was then considered "lost".
However, his short maneuver was not in vain. Nearly six years later, researchers have indeed acquired new information about the comet thanks to measurements from Philae's ROMAP magnetometer.
Concretely, when he tried to land, Philae hit the ground several times. First at its intended landing site, then at a second site, then at a third thirty meters away, where it finally came to rest. The latter would not be identified until almost two years later, when a camera attached to Rosetta, still in orbit, spotted Philae, hidden in the shadow of a ridge.
That said, since this episode, researchers have been working to determine the exact location of the second bounce. And for good reason, "the sensors of the Philae robot indeed indicated that it had penetrated the surface, thus likely exposing the primitive ice hidden under it" , explains Laurence O’Rourke, of the ESA, in a press release. These data collected, the researchers were finally able to analyze them.
In Nature magazine , the mission managers explain that they were able to measure both the depth of the imprint (25 centimeters) and the speed with which it was printed (three seconds). From there, they then estimated the compressive strength of the icy rock. And, surprise, this block of ice cream was incredibly fluffy .
“Philae's simple action has made us realize that this ancient mixture of icy dust, billions of years old, is extraordinarily sweet – fluffier than cappuccino froth » , continues Laurence O’Rourke, of the ESA, in a press release.
The new data also pointed out that the rock hit by Philae is quite porous. In other words, there is a lot of empty space between the ice and the dust grains. For Matt Taylor, also of the Rosetta project, this type of study is essential for future landing missions. “The fact that the comet has such a soft interior is really valuable information in terms of the design of the landing mechanisms, as well as the mechanical processes that might be needed to retrieve samples” .
