Philae Reveals Newest Details Of Its Comet

Rosetta, Philae and the comet. ESA/Rosetta/Navcam.

The results from a special lander sitting on top of a particular comet have been trickling toward Earth for the past few months, and they reveal greatly anticipated details about the icy body, called Churyumov-Gerasimenko.

You might remember the epic tale of the Rosetta Orbiter and its accompanying lander named Philae. These intrepid explorers have been shooting through the Solar System, chasing a comet that's whizzing toward the Sun. In November 2014, the Philae Lander was released from the Rosetta orbiter to land on the comet. 

The touchdown was a success, but there was no time to celebrate. As soon as Philae hit the surface it was off again, bouncing elsewhere before settling in a not-very-ideal location: the edge of a crater. This meant that the solar panels designed to charge the batteries were in too much shade to be effective. 

Reconstructed trajectories of Philae's bounce and landing by SONC (green) and ESOC (blue). ESA/ESOC/SONC.

Fortunately, even though the conditions for retrieving information were not ideal, scientists have been applying all of their ingenuity to discover everything they can about Churyumov-Gerasimenko. And the details are fascinating.

Philae's bouncy landing was thanks to the intended landing site being softer than anticipated. There is still information to be gleaned from this data: scientists can create theories about the structure of the comet based on how hard and far it bounced. Based on the trajectory, scientists believe that the landing spot was made up of two layers of material. The top layer, which Philae's feet touched, was a soft, granular surface around 0.25 meters thick, covering a harder layer below. The final landing site was about twice as hard as the intended landing site and as a result, only one leg was able to anchor itself on the surface. And only partially. These findings have been published in Science.

Tilman Spohn, from the Institute of Planetary Research, spoke with IFLScience about his findings on the mechanical and thermal properties of Philae. You can also read his team's findings published in Science.

Due to the unexpected landing location in which Philae ended up, the drill frustratingly didn't have enough power to pierce through the surface of the comet to discover the mineral composition in the ground. Spohn recalled to IFLScience, "We tried for three and a half hours to nail the base into the ground," before they gave up on the pursuit. The drilling activity was not fruitless, though. The inability to penetrate the surface still gave the researchers a lot of information to help them to figure out what properties the surface might have. Spohn said that the composition was probably similar to compacted snow, but "Glass foam is actually the best analogy" – the same substance that is used to insulate buildings.

He lamented that the lander ended up in a shadowy region as it doesn't just mean that data is relatively sparse, but also that the temperature measurements that they are calculating are all based in the shade. 

Comet on Jan 31 2015 (left) and Feb 3 2015 (right). ESA/Rosetta/NAVCAM – CC BY-SA IGO 3.0.

While sitting on its little comet, Philae has managed to identify 16 organic compounds and, incredibly, four of them have never been detected on a comet before. This is extremely exciting and could have significant implications for puzzling out how life on Earth began. Some scientists believe that it was comets that carried organic compounds onto Earth's surface. These compounds were then thought to be important for the chemical and biological evolution of Earth. The results can be found in Science.

Spohn ended on a positive note: "We still have some data in the pipeline that we haven't had a chance to evaluate, which includes the radiometer data while flying towards the comet, and then some more data across the comet." So even if Philae doesn't wake up again, there is still plenty of work to do!

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