The duck-shaped comet being tracked by Rosetta around our solar system is proving to be even more weird and wonderful than first thought, with a host of new photos and data flowing from the mission team.
These include the presence of what have been nicknamed ‘goosebumps’, which are lumps of material about three-metres in size that offer a tantalising clue as to how gas and dust may have clumped together in the early era of our solar system.
There is also a big crack in-between the ‘neck’ and the ‘body’ of the rubber-duck-shaped comet, more or less parallel with the head. The crack is about 500 metres long, and it’s not clear whether it has formed because of stresses from the outgassing of material below the surface, or some other unknown process.
There are also what are being described as dune-like formations on the comet, which is rather strange, because it has neither the gravity nor atmosphere for the kinds of processes that create dunes on planet Earth.
The dunes were probably formed by strong jets of gas travelling at 300 metres per second that push particles of dust away, and they then form into familiar bermed shapes.
The Rosetta team has been exploring comet 67P as they would a new island found in the middle of the ocean, and in keeping with the Ancient Egyptian theme of the Rosetta mission – as in Rosetta Stone – the 19 different regions have been named after Egyptian deities.
So comet 67P/Churyumov-Gerasimenko, is peppered with places called things like Imhoptel, Khepry, Ma’at and Hatmehit, making it arguably the least pronounceable body in the known universe.
The comet has been put on the cosmic weighing scales and it turns out that this 4.57 billion year old lump of dust and ice measures 21.4 square kilometres, and has a mass of 10 billion tonnes. Density is quite low, around 470 kg/m3, which is about the same as cork.
Of course there are many traps and pitfalls when describing the comet in everyday language, not least because we humans are limited in our vocabulary. Using terms such as cliff, dune, crevasse and boulder can be misleading – bear in mind that this is a truly alien world, nobody has ever flown this close to a comet for so long, and it really is completely unlike the planets that surround us.
The detail of the discoveries and the wondrous photos of outgassing jets will continue to flow throughout 2015, as Rosetta flies down to under 10 kilometres away all year.
One of the highlights will be what’s called perihelion, when 67P comes down to its closest approach to the sun, somewhere between the orbital planes of Earth and Mars, and then heads back into the outer solar system. At this time it could become very active, and all kinds of interesting molecules could be blown out from below the surface by the solar radiation.
Another highlight could be the reawakening of that plucky robot probe Philae, which became the planet’s favourite space adventurer last year when it bounced down on the comet surface and eventually landed in the shade of a cliff. As the comet gets closer to the Sun, and its ‘seasons’ change, there is a chance Philae could warm up and get back to work.
More details on the Rosetta results can be found in a special edition of Science Magazine