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Rosetta the comet hunter arrives at its target

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Rosetta the comet hunter arrives at its target


Space history is being made in our solar system this summer as ESA’s Rosetta spacecraft catches up with a comet and begins to orbit around it for the very first time. The space probe has spent a decade flying around the planets, gaining enough speed and the right trajectory to rendezvous perfectly with the icy mass of comet 67P/Churyumov-Gerasimenko. This week it moves into position, and becomes the first man-made object ever to fly alongside a comet as it speeds towards the Sun, grabbing some stunning photographs and revealing science data in the process.

Those pictures have already shown the comet is quite unlike the scientists had expected. When the Hubble Space Telescope shot a distant view of 67P over a decade ago it looked like a squashed football – pretty much the ‘normal’ shape of the average comet – but the images from Rosetta’s cameras taken in the past few days have revealed a very odd comet that looks quite a lot like the shape of a rubber duck.

The scientists still aren’t sure why it has such a strange form, but a few different theories have already emerged. For example, it could be that 67P was made from two lumps of primordial material colliding in the early era of our solar system, rather than one lump of aggregated material, or it could be that an impact with another body could have deformed it, or it may be that there is a difference in mass and therefore gravity in the comet that means it is such a weird shape.

Currently Rosetta is flying close to 67P way out near Jupiter – you can see it’s rather amazing journey in this interactive map from ESA – and it will follow the comet as it approaches the inner solar system, observing how the ice and dust of the comet is heated by the Sun and in so doing, getting a much better idea of what’s inside. That will help scientists to better understand what our early solar system was made from.

The daring, complex and pioneering nature of the Rosetta mission means that it is now considered one of the most exciting missions of recent space history, and the saga of this particular spacecraft is likely to become even more thrilling later in 2014. In November, if everything goes to plan, Rosetta will release a small lander, called Philae, which should touch down on the surface of 67P, drill itself into the ice, and then start taking photographs and scientific measurements on the actual surface of the comet.

Before that extraordinary maneuver can even be attempted, the flight engineers and scientists will have to find a landing spot, a tricky proposition considering the venting of gas and dust from the surface as the comet warms, and the dangers of falling into a crevice in the dark, icy surface, never to be heard from again. If Philae does what its designers hope it can do, it should be the most outstanding technical achievement in space flight since Curiosity’s ‘space crane’ stunt on Mars, and with a much less docile subject than the well-mapped wastes of the red planet.

Why ‘Rosetta’?

Rosetta is a nice word to write and a nice name to say, and in terms of internet search terms it’s pretty effective, but that’s not why it was chosen for this spacecraft. In the British Museum in London lies something called the ‘Rosetta Stone’ a slab of volcanic basalt that is widely seen as the key to unraveling and decrypting the civilization of ancient Egypt. The stone effectively gave French and British scholars the information they needed to piece together the history of that culture. Philae is the name of the island in the Nile on which it was found in 1799.

So where is this leading? Well, comets are seen as relics of the early formation of the planets, and there are many scientists who believe that comets brought much of the water and building blocks of life to the early Earth. So ESA believes that if we can truly grasp what comets are made of then we have a much better chance of understanding the secrets of our origins by piecing together what kinds of matter were swirling around our Sun 4.6 billion years ago. That was a time when no planets had yet formed, but instead our solar system was full of icy comets and rocky asteroids spinning around our star, carrying all the bits and bobs that would eventually make up what we see around us today, including you, me and the water cooler. So, Rosetta could be key, or maybe even the key, to finding out where we came from.

Rosetta certainly isn’t the first mission to get close to a comet – in fact ESA’s Giotto mission flew right past Halley’s comet in 1986, just under 600km from the surface, and in 2005 NASA pulled off a Hollywood blockbuster stunt by smashing their Deep impact spacecraft into comet Tempel 1. Six years earlier the American space agency had also used a spacecraft called Stardust to return comet dust to Earth, with intriguing results that revealed the presence of amino acids.

They were all groundbreaking missions, but none of them achieved the combination of velocity and trajectory that Rosetta has managed by swinging by Earth and Mars a few times, right into the flight path of 67P. Now the race is on at the European Space Operations Centre in Germany to make the past 10 years of effort to get there worthwhile, to collect some unique data and perform some outstanding science in the nominal 12 month window before Rosetta is supposed to be retired.

Live updates about the Rosetta mission

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