The Rosetta orbiter could capture striking images as the comet reaches perihelion

Rosetta mission prepares for closest approach to Sun

Scientists working on the Rosetta space mission are preparing for drama as the comet they are observing reaches its closest point to the Sun tomorrow.

As Comet 67P/Churyumov-Gerasimenko's orbit takes it nearer to the sun, rising temperatures cause its activity to increase as ices vaporise and gas jets burst out from its interior and tomorrow will bring it within 115.5 million miles from the sun, causing temperatures on its surface to peak.

The most dramatic event that could happen around the time the comet comes nearest to the Sun, an event known as perihelion, is the 'duck-shaped' comet snapping in half at the narrow 0.6-mile-wide 'neck' joining its two lobes.

A 500-metre-long fracture has already been identified in the neck where such a break could occur as interior forces build up with the rising temperatures, and if it does scientists expect the orbiting Rosetta spacecraft to send back dramatic images.

Activity has been on the rise in recent weeks. On July 29, instruments on the European Space Agency orbiter recorded an eruption of gas and dust emerging from the side of the neck strong enough to push away the incoming solar wind, the stream of magnetically bound energetic particles from the sun.

Dr Carsten Guttler, Osiris team member at the Max Planck Institute for Solar System Research in Gottingen, Germany, said: "This is the brightest jet we've seen so far. Usually the jets are quite faint compared to the nucleus and we need to stretch the contrast of the images to make them visible, but this one is brighter than the nucleus."

Measurements showed that after the outburst, levels of carbon dioxide around the comet doubled and the amount of methane went up four times.

Dr Kathrin Altwegg, another Rosetta scientists at the University of Bern in Germany, said: "We... see hints of heavy organic material after the outburst that might be related to the ejected dust. But while it is tempting to think that we are detecting material that may have been freed from beneath the comet's surface, it is too early to say for certain that this is the case."

All this is happening around the Philae lander that made history after being dropped on to the surface of the comet from the orbiter on November 12 last year.

After bouncing away from its targeted landing site and ending up in partial shadow that deprived its solar panels of sunlight, the lander used up the last of its battery power and went into hibernation three days later.

The lander 'woke up' in June as the comet travelled closer to the sun and sent back valuable scientific information, including the presence of organic chemicals, but then fell silent again and nothing has been heard from it since July 9.

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