Astronomie - Staubwirbel auf Mond entdeckt


Scientists in the UK have solved a long-standing mystery on the Moon - and their solution could help develop a shield to protect astronauts against deadly radiation.
A team from RAL Space at the Rutherford Appleton Laboratory in Oxfordshire looked at so-called lunar swirls - patches of pale soil on the Moon, some several tens of kms across, for which there had been no ready explanation before.
They identified that small scale magnetic bubbles - miniature versions of the field that protects the Earth - were deflecting the blast from the solar wind that was bombarding the Moon.
The scientists, led by Dr Ruth Bamford, combined the space data with experiments in a "solar wind tunnel" to construct an experimental magnetic shield that might protect explorers in their journeys between the planets.
Radiation from powerful solar flares, which can occur at any time, are one of the biggest hazards confronting long-distance space travellers because of the high levels of radiation they can produce.
There are already safety areas on the International Space Station where astronauts can shelter. But on a journey to Mars the prospect of bad space weather is a very worrying one.
The RAL team realised that understanding just how the "mini-magnetospheres" on the Moon produce a cavity in the solar wind to drive away the solar wind could help them design a mechanism to protect space explorers. Scientists at the University of York in the UK have now managed to create similar "bubbles" in the laboratory.
Dr Bamford said: "Close to the moon's surface, the strength of a magnetic anomaly is likely to be very irregular, featuring overlapping "cavities" and "gradients". Over an estimated 3.8 billion years these anomalies would have been deflecting the solar wind particles streaming in from space, slowly creating these amazing patterns, which can be clearly seen on the lunar surface today.
"We still need to determine quite how effective this mechanism would be at deflecting the real hazardous higher energy particles. The jury is still out on that one, but such an active shield could make the difference between survivable and certain death for astronauts on their way to Mars."
Dr Bamford added: "When we first tried the experiment in the Solar Wind Tunnel and it worked, it was very exciting. The active force which deflect the solar wind particles is electric not magnetic. The electric field is created naturally by the edges of the moon's magnetic 'bubbles".

"What matters is the "gradient" in the magnetic field, rather than the overall size of the magnetic bubble. So they can be as small as you like - as long as the gradient is steep enough ".

Dr Bamford has long been experimenting on building a protective shield, using a shop-bought magnet for earlier tests. She told this writer: "These initial experiments have shown promise and it may be possible to shield astronauts from deadly space weather. NASA have shown a lot of interest in our work. We've shown this is possible and not just science fiction. It is all very encouraging."

Dr Bamford, who thought it might take 15-20 years to develop a full-scale model for a real spaceship, pointed out that science fiction shows had got their ideas for defence fields from the Earth's own protective field. She told me: "The shields in Star Trek were inspired by the magnetosphere in the first place."

The most striking lunar swirl is called Reiner Gamma and can be seen from Earth with a good telescope. The picture above was taken by NASA's Lunar Reconnaissance Orbiter probe in orbit around the Moon.

Quelle: SEN