Six years after bouncing across Comet 67P/Churyumov-Gerasimenko—nicknamed 'Tchouri'—the Philae lander sank into surface ice as fluffy as cappuccino froth, according to a new study published Wednesday.
In 2014, after more than a decade in space, the European Space Agency's (ESA) Rosetta mission arrived at its target: Comet 67P/Churyumov-Gerasimenko, over 500 million kilometers from Earth. A key goal was to softly land the Philae probe on the comet's surface. On November 13, Philae made history as the first human-made object to attempt such a landing.
The landing didn't go smoothly. Philae bounced off the surface, ending up in a shaded spot with insufficient sunlight for power. ESA eventually ceased contact attempts, declaring the lander 'lost.'
Yet Philae's brief activity yielded valuable data. Researchers recently analyzed readings from its ROMAP magnetometer, gaining fresh insights into the comet nearly six years on.
During descent, Philae struck the surface multiple times: first at the target site, then a second spot, and finally a third 30 meters away, where it settled. This final location wasn't pinpointed until nearly two years later, when Rosetta's orbiter camera spotted it tucked in a ridge's shadow.
Scientists have since honed in on the second bounce site. "Philae's sensors showed it penetrated the surface, likely exposing pristine ice beneath," says Laurence O'Rourke of ESA in a press release. This data enabled detailed analysis.
Published in Nature, the study details Philae's 25-centimeter-deep imprint, formed in three seconds. From this, the team calculated the ice's compressive strength—and found it incredibly fluffy.
"Philae's encounter revealed this billions-year-old icy dust mix is extraordinarily porous—fluffier than cappuccino froth," O'Rourke adds.
The ice-dust layer is highly porous, with ample voids between grains. Rosetta project scientist Matt Taylor notes: "This soft interior is crucial for designing future landers and sample-retrieval mechanisms."
