Rosetta ready to unlock comet’s secrets
After more than a decade in pursuit, clocking up four billion miles and five loops around the Sun, the Rosetta spacecraft closed in on its target yesterday, becoming the first in history to go into orbit about a comet.
With a thrust of its engines, the European spacecraft was kicked into the first leg of its triangular orbit about the duck-shaped comet at 10am yesterday, although scientists had to wait a further 25 minutes — the time taken for the probe’s faint signal to reach Earth — to learn that the manoeuvre had been a success.
The comet, called 67P/Churyumov-Gerasimenko, or “Chury”, lies 252 million miles (405 million km) from Earth, between the orbits of Jupiter and Mars, and is rushing towards the inner solar system at nearly 34,000mph (55,000 km/hr).
The craft will now spiral inwards towards Chury until it is less than a mile away and close enough to release a robotic lander that will float down on to the surface.
Jean-Jacques Dordain, director-general of the European Space Agency (ESA), said: “We are delighted to announce finally ‘we are here’. Europe’s Rosetta is now the first spacecraft in history to rendezvous with a comet, a major highlight in exploring our origins. The discoveries can begin.”
The mission will ultimately examine the chemical make-up of the comet in unprecedented detail and could reveal whether so-called dirty snowballs could have originally brought water and the basic building blocks of life to Earth billions of years ago.
The latest phase of the mission began in January, when the probe successfully “woke up” from a three-year period of hibernation, during which it was so far from the Sun that the little solar energy available was required to warm its internal computers. The coming months will hold further nail-biting moments for the scientists involved.
Much of the equipment aboard the lander has been in a dormant state during the ten-year journey and scientists say that it is impossible to be completely confident that each component will switch on again smoothly. These components include small harpoons that will tether the lander to the surface of the comet, to prevent it from bouncing off, and drills in its legs that will secure it firmly.
Richard Holdaway, director of Rutherford Appleton Laboratory Space, said: “It’s like an old car on a winter’s day. Most of the time it works, but occasionally it doesn’t. That’s the sort of uncertainty we’re dealing with.”
The latest close-up images hint at other challenges that will be faced, when Philae, the fridge-sized lander, is dropped on to the surface in November. The images reveal the comet is composed of two distinct segments joined by a “neck”, giving it a duck-like appearance, and it has a rugged surface littered with boulders and troughs. The next two months will be spent assessing the comet for potential landing sites.
Matt Taylor, ESA’s Rosetta project scientist, said: “Our first clear views of the comet have given us plenty to think about. Is this double-lobed structure built from two comets that came together in the solar system’s history, or is it one comet that has eroded dramatically and asymmetrically over time?”
It will not be until Philae touches down that scientists learn whether the surface is ice-hard or dusty.
“The landing is going to be pretty hairy,” Professor Holdaway said. “And the chance of missing it is finite, albeit very small.”
As the comet travels closer to the Sun, it is likely to become more active, warming up and releasing more dust and other compounds accumulated on its surface. Sensors aboard Rosetta and Philae will analyse these, looking in particular for organic compounds that indicate that comets could have initially seeded Earth with the building blocks for life.
Ian Wright, professor of planetary sciences at The Open University, said: “We will be looking for evidence recorded in remnants of debris that survived the processes of planet formation. This is not merely a period of pre-history, but one that pre-dates the origin of life itself. Our quest is to gain insights into this transitional era, which took place more than 4.5 billion years ago.
http://www.thetimes.co.uk/tto/science/a ... 168813.ece
