Rosetta probe studies released, revealing fullest picture of comet yet

Space News

From the ‘frozen primordial soup’ of organics on the comet to new pictures, the discoveries made during the Philae lander’s first days have been published.

The Philae lander may have spoken its final words, but with the data beamed back to its mothership, Rosetta, scientists have painted the fullest picture yet of comet 67P/Churyumov-Gerasimenko.

1024Comet 67P/Churyumov-Gerasimenko, in a pictures taken during Philae’s descent by the ROLIS instrument on board the lander. This view is of the surface from approximately 3 km away

Born from the detritus of the primordial solar system more than 4.5 billion years ago, the icy comet has a fluffy coating over a hard-grained surface pocked with gas-spewing sinkholes. Yet it is more nothing than something: its interior is at least 75% empty space.

The body is rich in organic molecules, which if delivered to a hospitable enough planet, might play a leading role in the process that turns simple chemicals into replicating molecules and ultimately rudimentary life.

Researchers on the European Space Agency mission published seven papers on Thursday in the journal Science that bring together the discoveries made in the lander’s first three days on the comet, before its batteries faded.

Stephan Ulamec, Philae’s project manager at the German Aerospace Centre in Cologne, told the Guardian that despite the lander bouncing off the comet when its harpoons and retrorocket failed to fire, the probe had a lucky encounter.

The moment the lander touched down, its feet sank into a fluffy layer about 20cm deep, and bounced sideways for more than a kilometre. Mid-leap, it clipped the side of a giant crater, which changed its course towards the hard, rough terrain that became its final resting place.

“It was good we hit the crater rim. If we had carried on, we would have fallen into the dark side of the comet, into an area that wasn’t even on the map in those days,” Ulamec said. “That would have been really bad. It would have been a fair chance to lose it and certainly not get any images.”

From its more illuminated spot, the probe’s seven cameras captured panoramic views of the fractured surface marked with reflective rock structures and dust grains. There is evidence of erosion, with boulders surrounded by dips in the surface that look similar to tail wind depressions caused by wind on Earth.

1867The data has revealed the exact trajectory and timing of the lander’s descent, the stages of which are shown here (excluding the final hop, which scientists believe was just a few metres).

Serendipity played a role in the mission’s success. When Philae touched down for the first time, it knocked up a cloud of cometary material. Some got lodged in the exhaust pipe of an instrument called COSAC and warmed up enough to vaporise. As the Philae lander reached the height of its bounce, 150 metres above the surface, COSAC sniffed the vapours from the comet grains and found water, carbon monoxide and a rich brew of 14 organic chemicals. Four of them, methyl isocyanate, acetone, propionaldehyde and acetamide, had not been seen on comets before.

“It was not planned like that. We wanted to drill samples from the consolidated soil with all the organics nicely frozen in place,” said Fred Goesmann, the lead scientist on COSAC at the Max Planck Institute for Solar System Research in Göttingen.

Researchers at the Open University in Milton Keynes found material from the same cloud had fallen into their Ptolemy instrument. The found evidence for polyoxymethylene, a polymer that is formed with the help of radiation.

Ian Wright, the lead scientist on the Ptolemy instrument, describes the organics found on the comet as a “frozen primordial soup”, but concedes some colleagues might not agree. “Potentially, that is what we are talking about, but I’ll get pilloried for saying so,” he added.

“If you were to put these materials on the surface of a primitive body like Earth, and give them the right amount of heat and whatever else is required, conceivably, you could form life,” he said.

Measurements taken from the surface of the comet show that daytime temperatures vary from a chilly -143C (-225F) to an even chillier -183C (-297F).

The orbiting Rosetta spacecraft dropped Philae onto the comet’s surface in November 2014, marking the first time a spacecraft had touched down on a comet. Philae bounced twice before coming to rest on its side near a cliff on the rim of a crater. The lander went to work for three days before its batteries ran out.

Mission scientists have not heard from Philae since 9 July, dampening spirits at the European Space Agency which were riding high after the craft awoke from a 7 month slumber in June. The lander called home after its solar panels captured enough sunlight to provide power to its systems. It is unclear why it fell silent again, but the probe may have been pushed into an awkward position by gas and dust now billowing from the comet’s surface.

Philae is not in good shape. One of its two receivers is dead, and one of its two transmitters is on the blink. Scientists on the mission are unsure if they will ever hear from the lander again. Goesmann confessed that he lost a five Euro bet that Philae would never wake up after its batteries ran out. “I’m very bad as a prophet, but I hope we hear more,” he said. If Philae had landed where mission scientists had intended, it would have died from overheating months ago.

Rosetta has swept around onto a different orbit to survey the southen hemisphere of the comet, which had been in darkness until recently. That will reveal more about the comet, but makes it harder to re-establish links with Philae.

“At the moment Rosetta is on the southern hemisphere, which leads to bad opportunities for lander communications, but after 8 August the situation should be better again,” he said. “Let’s keep our fingers crossed.”