Space Probe Philae Impact Revealed Surprisingly 'Fluffy' Comet Interior

When the Philae space probe hit a comet, it scraped open a window to bare, ancient, 'fluffy' ice.
Brad Bergan
The photo credit line may appear like thisESA / Rosetta / NAVCAM

After years of analysis, scientists working on the European Space Agency's (ESA's) Rosetta mission have confirmed the location where the spacecraft made its second and penultimate contact with the comet's surface — where Philae scratched the surface open and exposed ice from the comet's formation, which looks like a bright, skull-like surface with the consistency "fluffier than cappuccino froth," according to a new study published in the journal Nature.


Space probe Philae's comet impact revealed 'fluffy' interior

When the space probe Philae impacted the comet "67P/Churyumov-Gerasimenk" in 2014 — it bounced a mile up into surrounding space, then fell again, tumbling and rolling across the comet's surface, with one metallic leg left sticking up embarrassingly into the "air."

The comet interior was revealed when Philae pressed its top side and the sample drill housing into an icy crevice in a black rocky area blanketed in carbonaceous dust. When it scratched the surface open, it exposed ice protected from the Sun's radiation since the formation of the comet.

The bright icy surface appeared with an outline not unlike a skull, which gives away the space probe's point of contact with the comet, according to a blog post on the German Aerospace Center's (DLR's) official website.

Philae Creates Eye of Skull
The haunting skull-like shape was created when Philae impacted the comet. Source: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA; O'Rourke et al (2020)

Mystery of Philae's final comet landing finally solved

Before this latest discovery, scientists only knew of the existence of a second point of impact after the rebound — the location where it came to rest and where it was eventually rediscovered toward the end of the Rosetta mission in 2016.

"Now we finally know the exact place where Philae touched down on the comet for the second time. This will allow us to fully reconstruct the lander's trajectory and derive important scientific results from the telemetry data as well as measurements from some of the instruments operating during the landing process," said Jean-Baptiste Vincent of the DLR Institute of Planetary Research, who was part of the recently published study in Nature.

"Philae had left us with one final mystery waiting to be solved," said Laurence O'Rourke of the ESA, who is also the lead author of the study. The scientists in the study wanted to complete a multi-year search for "TD2" — touchdown point two. "It was important to find the touchdown site because sensors on Philae indicated that it had dug into the surface, most likely exposing the primitive ice hidden underneath," added O'Rourke.

In the last few years, the search for the spacecraft's final location went forward like a hunt for a needle in a haystack — while several images and datasets from the landing area were reviewed.

Magnetometer gave the space probe's location away

Scientists have searched for spots of bare ice in regions on comets using high-resolution images collected via the Optical, Spectroscopic and Infrared Remote Imaging System (OSIRIS) instrument — which the Max Plank Institute for Solar System Research (MPS) developed before it was loaded onto the Rosetta orbiter.

However, the evaluation of measurements carried out via the ROsetta MAgnetometer and Plasma monitor (ROMAP) — created for the Philae lander under the purview of the Technical University of Braunschweig — ultimately clued the scientists into the right direction, read the DLR blog post.

So it seems the comet's ice — stored inside for 4.5 billion years — is so soft it's fluffier than the froth on a cappuccino, the whitecaps of water waves meeting the coast, or the foam of a bathtub. Scientists have learned how a lot from the crash of one space probe. As the ESA, NASA, and several other private and public space agencies expand space missions into deep space, the discoveries to come are without end.


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