Prior to going into hibernation mode, the Philae lander hurriedly conducted a number of experiments and sent its findings back to Earth. Preliminary analysis shows that the icy and dust-covered comet contains organic molecules. It's a cool discovery, no doubt, but one that shouldn't be exaggerated in terms of its importance.
Obviously, people are excited by the discovery of organic molecules because it feeds into the idea that comets may have delivered the chemical prerequisites for life — compounds that could have kindled the genesis of life on our planet. Indeed, scientists aren't exactly sure how life arose on primordial Earth, leading some to suggest that comets and asteroids may have been responsible for delivering the key components required to spark and sustain life, like crucial minerals or dormant microbial life.
Not What You Think It Means
The trouble is the ESA has not revealed which organic molecule was discovered. And that's important because, as any student of organic chemistry knows, "organic" in this context simply means a molecule with one or more carbon atoms somewhere in it. And while life depends on organic compounds, there are plenty of organic compounds devoid of life, like methane and methanol gases — common chemical reactions that really have nothing to do with living organisms.
What's more, it's already well known that organic compounds are abundant in the cosmos.
It would be a different story, however, if Philae discovered a set of specific organic molecules, like amino acids — the building block of proteins. We'll just have to wait for the ESA to reveal more, but until then we should temper our enthusiasm about this latest discovery.
Dust Covered Ice
In terms of other findings, Philae's MUPUS instrument recorded a temperature of –153°C before Philae was deployed. Then, during the descent, the sensors cooled by about 10°C over a period of roughly half an hour. ESA scientists speculate that this was either due to radiative transfer of heat or because the probe was pushed into a cold dust pile.
It also turns out the the comet is very, very hard. When the probe started to drill, it wasn't able to make more than a few millimeters of progress.
"If we compare the data with laboratory measurements, we think that the probe encountered a hard surface with strength comparable to that of solid ice," noted Tilman Spohn, principal investigator for MUPUS.
Looking at the results, it appears that the upper layers of the comet's surface consist of dust that's 10–20 cm ( 4-8 inches) thick, overtop strong ice or ice and dust mixtures. Deeper, the ice is probably more porous, as the overall low density of the nucleus would suggest.