Expert opinion: The European Space Agency's 'Rosetta' mission

Dr Dan Brown, an astronomy expert at Nottingham Trent University, discusses the European Space Agency's 'Rosetta' mission, which is due to arrive at comet 67P/Churyumov-Gerasimenko on August 6.

Dr Dan Brown, an astronomy expert at Nottingham Trent University, discusses the European Space Agency's 'Rosetta' mission, which is due to arrive at comet 67P/Churyumov-Gerasimenko on August 6.

Rosetta is a European Space Agency mission launched in 2004, with a space probe sent to explore the comet 67P / Churyumov-Gerasimenko (67P) in close proximity. Rosetta will be the first probe to orbit a comet and deploy a robotic lander called Philae to analyse its surface. The probe will continue analysing the comet while it becomes active and flies past our Sun.

67P was discovered on 11 September 1969, at the Alma-Ata Astrophysical Institute by Klim I. Churyumov and Svetlana I. Gerasimenko. The comet orbits our Sun every 6.5 years and will reach its closest point to the Sun in August 2015.

It is a large dirty snow ball, not untypical for a comet, and is approximately 3.5km x 4km.

The comet also appears to be a contact binary of two larger bodies that make it quite irregular in shape, similar to a rubber duck, and is a challenging gravitational environment to manoeuvre in.

Comets are dynamic, both in their unstable orbital path around the Sun, and their activity caused by warming through the Sun.

At its furthest from the Sun, 67P is just beyond the orbit of Jupiter, and at its closest just inside the orbit of Mars. Close encounters with Jupiter resulted in 67P reaching the orbit of Mars since its discovery.

As Rosetta approaches, the comet has just passed its most inactive phase and is beginning to melt ever so slightly, generating a haze - or halo - of gas around its main body. However, even this is not predictable as the comet stopped producing its halo just before Rosetta arrived, illustrating that we need to learn more to understand these dynamic objects.

67P was formed during the very early period of our solar system and harbours inside it the chemical composition of what made our solar system, frozen in time. Analysing the comet's composition will help us to understand our early solar system and what role comets might have played in creating habitable planets.

The lander Philae will analyse surface samples after touching down on 67P from the beginning of November 2014. To land on such a light weight and crumbly snowball Philae uses a harpoon to anchor itself to the surface.

The activity of a comet can look spectacular and beautiful from Earth but is a major hazard when orbiting the main cometary body. Even though we will not be able to see the comet with the naked eye on Earth, 67P's activity will be substantial. This resulted in Rosetta arriving at the comet now and deploying the lander in November, even though the comet is still nearly a year from its solar encounter.

The ten-year voyage to catch 67P so far from the Sun was required to allow the probe to safely establish orbit and carry out its survey work, as well as landing Philae on its surface before the snowball starts erupting in massive gaseous fountains of sublimating ice.

Find out more about the mission, including recent results and what they can tell us, at Nottingham Trent University's Open Dome Event, Landing on a Comet: The Rosetta Mission - on 27 October.

Dr Dan Brown
School of Science and Technology
Nottingham Trent University

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Expert opinion: The European Space Agency's 'Rosetta' mission

Published on 5 August 2014
  • Category: Press office; School of Science and Technology

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