A weak comet and a sandblasted spacecraft: NASA expert on the Philae Rosetta mission

This article originally appeared on Culture24.

NASA scientist who helped plan Rosetta mission says ancient comet chosen to prolong probe's lifespan before sandblasting death

The comet which scientists are hoping to glean secrets of the universe from has been chosen because of its ancient, fragile state, according to a Leicester scientist who was involved in the first ever mission to study a comet.

Professor Stanley Cowley, who is now part of the University of Leicester's Department of Physics and Astronomy, was part of the NASA International Cometary Explorer team which spent four years analysing the data returned by a spacecraft on the plasma tail of Giacobini-Zinner.

Beginning in 1985 in a bid to study the interactions between comets and the solar wind, they went on to oversee the fleet of Russian and Japanese satellites at the high-profile Halley comet a year later, as well as the European Giotto mission which went to Greig-Skjellerup in 1992.

“The Philae lander is the first attempt to land a spacecraft on the surface of a comet nucleus,” says Professor Cowley, who has a keen interest in the £800 million Rosetta mission, having assisted its planning stages.

“The main new thing here is the ability to directly sample the surface material using a nine-inch drill, and to analyse that material using a series of experiments looking at the chemicals present.

“One key thing about Rosetta is the matching of the orbit of the spacecraft with that of the comet.

“The satellite has been put into a close orbit around the nucleus, and will now move with it as the nucleus moves inward towards the Sun.

“As the nucleus warms up as it gets closer to the sun – more-or-less ‘room’ temperature at its closest point - Rosetta will be able to observe the beginning and evolution of the outgassing of volatile components from the nucleus – principally water gas from the deep-frozen ice within.

“Comet 67P/C-G is an old and very weak comet, purposely chosen so that the material – the water, gas and embedded dust that comes out of the vents at 1km per second – doesn’t sandblast the spacecraft to death too quickly.”

Although the lander initially bounced off the comet, the European Space Agency re-established contact with its craft on Thursday morning. Mission control waited 28 minutes and 20 seconds to discover that the landing had succeeded, and experts are now receiving pictures of the comet, which will pass closest to the sun in August 2015.

“Comet impacts are thought to have been one of the principal means by which water was delivered to the early Earth, around 3.6 billion years ago, possibly contributing half the water in our oceans,” says Professor Cowley.

“The other half would have come from the Earth’s interior.

“Furthermore, the comet material is also known to contain simple organic molecules which may also have seeded Earth with the material from which life emerged.

“So there are lots of good reasons to look at these objects carefully.”

In 1994, Professor Cowley proposed the inclusion of a magnetic field instrument on the Rosetta satellite, which became one of a bank five hi-tech instruments onboard the satellite.

He is currently working on NASA’s Cassini mission to Saturn and the Agency’s exploration of Jupiter’s moons. A team from the university also used x-rays to examine the cloud of debris caused by a NASA Deep Impact mission which struck the surface of a comet at high speed in 2005.

“There has been quite a lot of work prior to Rosetta, including direct dust collection and return to Earth and impactors, as well as images of the nucleus and sampling of the dust and gas emitted, and the resulting plasma interaction with the solar wind.”

Rosetta has reached a speed of 34,000 mph to fly in formation with the comet.

“The wider context is that comets, like 67P/C-G, represent bodies which were 'left over', essentially unprocessed, from the formation of the solar system some 4.5 billion years ago,” points out Professor Cowley.

“It is therefore an interesting relic from that otherwise inaccessible epoch.”

What do you think? Leave a comment below.

More on the Rosetta mission:

In Pictures: European Space Agency's Philae Rosetta comet probe thrills scientists

Archaeologists and astronomers in Philae Rosetta mission to comet 261 million miles away

Source: http://www.culture24.org.uk//science-and-nature/art506202-a-weak-comet-and-a-sandblasted-spacecraft-nasa-expert-on-the-philae-rosetta-mission