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Master of Scaremonies
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Space mirrors could create Earth-like haven on Mars
14 November 2006
NewScientist.com news service
David Shiga

An orbiting array of reflective balloons focuses sunlight onto the surface of Mars, providing extra heat and solar power for human colonists.

Mirrors in orbit around Mars could create Earth-like conditions on a small patch of the planet's surface, according to a NASA-funded study. The extra sunlight would provide warmth and solar power for human explorers, but some experts say the mirrors may be hard to deploy.

Scientists and science-fiction authors have long dreamed of turning Mars into a more Earth-like planet for future human colonists. The process, called terraforming, involves thickening Mars's atmosphere and increasing its temperature. But schemes to transform the entire planet would take centuries and would require enormous resources.

Now, Rigel Woida, an engineering student at Arizona State University in Tucson, US, is investigating the possibility of "terraforming" just a small patch of the planet's surface by focusing sunlight on it from orbiting mirrors.

He received $9000 to study the idea from the NASA Institute for Advanced Concepts (NIAC) in Atlanta, Georgia, US.

The concept calls for 300 reflective balloons, each 150 metres across, arranged side-by-side to create a 1.5-kilometre-wide mirror in orbit around Mars.
Balmy conditions

The mirror would focus sunlight onto a 1-kilometre-wide patch of Mars's surface. This would raise the temperature in this patch to a balmy 20° Celsius (68° Fahrenheit) from Mars's typical surface temperature of between -140° C and -60° C (-220° and -76° F).

The extra warmth would mean the astronauts would not need heavily insulated suits or living quarters, allowing them to work more easily. The extra sunlight would also boost power from solar cells.

And the higher temperature would melt any water ice on the ground. This could make precious liquid water available for astronauts to drink, and the water could also be used as a raw material to produce rocket fuel for the journey home, Woida says.

"The greatest hold-up to exploration, terraforming and colonisation of Mars is the lack of available materials," he told New Scientist.

He says astronauts could maximise the amount of available water by warming up a region that includes a frozen lake, such as the one near the planet's north pole that was imaged by Europe's Mars Express spacecraft (see Frozen lake shines bright in Martian crater ).
Dangerous radiation

Margarita Marinova of Caltech in Pasadena, US, who is not involved in the study, says the extra solar power would greatly benefit future Mars missions. "This would be quite useful for many types of missions - both robotic and human," she told New Scientist.

She cautions, however, that deploying objects in space can be challenging, citing an experimental tether that broke during deployment from the space shuttle in 1996 and the failure of solar sail experiments. The orbiting mirror for Mars "is not an easy project by any means", she says.

Woida points out another potential problem. If not carefully designed, the mirrors could focus harmful high-frequency radiation like gamma rays onto the surface.

Mars's thinner atmosphere would not filter these out like Earth's does, so the balloons would have to be coated with materials that would reflect only visible and infrared light, he says.

In his concept study, Woida will work out the structural details of the balloons and study how much extra light from the reflectors reaches the Martian surface.
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