Published online 18 October 2007 | Nature | doi:10.1038/news.2007.175


Crashed spacecraft yields data

Scientists pick out solar-wind samples from the pieces of the Genesis mission.

Stunt helicopters had to get out of the way when Genesis crash landed.USAF 388th Range Sqd / NASA

An ill-fated spacecraft that unintentionally crashed into the deserts of Utah in 2004 is yielding results to the scientists who carefully picked up the pieces.

Researchers have been able to salvage usable material from the Genesis mission, whose aim was to collect samples from the solar wind and bring them safely back to Earth. The results, picked from millimetre-sized shards of the spacecraft's detectors, provide a snapshot of the early Solar System, and will feed into models that outline how our planet’s atmosphere evolved. “Great measurements can be made on small objects,” says Genesis scientist Roger Wiens of the Los Alamos National Laboratory in New Mexico.

The Genesis mission spent 27 months in space with its innards spread open to the Sun, gathering tiny samples from different types of solar wind. Its delicate and contamination-sensitive collectors were due to be returned to Earth using an unusual technique — Hollywood stunt pilots were enlisted to swoop by in a helicopter and catch the falling capsule. But the craft’s parachute did not open, and the careening craft ploughed a hole into the desert. Observers were initially devastated that the spacecraft had crashed, but researchers soon realized that data could be salvaged — albeit more slowly and with more effort.

“The landing didn't help”

Roger Wiens

“We had originally hoped we could publish a series of papers within a year,” says Wiens. It has taken much longer than that, but a series of four papers have now been published in Space Science Reviews1,2,3,4, and a fifth follows this week in Science5. A preliminary paper was also published last year6.

The team remains hopeful that they will soon be able to complete the main goal of their original mission: solving the mystery of the unique isotopic signature of different objects in our galaxy.

Blowing in the wind

The Science paper contains a study of the ratio of different isotopes of neon and argon obtained from samples of three types of solar wind: fast, slow, and coronal mass ejections from the Sun’s surface. The researchers conclude that these ratios are essentially the same in all three types of wind. This is good news: it indicates that the elements of main interest to the researchers have the same isotopic signature in the solar wind as in the Sun itself.

That’s useful because the outer layer of the Sun is thought to provide a picture of isotopic ratios in the very early Solar System, before stars or planets were formed. "There was a concern that there would be a difference between the solar wind and the Sun," says Kevin McKeegan, a Genesis scientist from the University of California, Los Angeles, who will attempt to measure oxygen isotopes from the craft's samples.

The isotopic ratios of neon and argon are not in themselves very surprising — scientists already had a fairly good measure of these values from previous missions, including one low-tech scheme that laid out a screen on the Moon to collect solar-wind samples. But they improve by a factor of 60 the precision with which the argon isotope ratio is known. This will be useful for researchers who model the early Solar System to work out processes such as how Earth’s atmosphere formed.

Gritty science

There is heavy contamination of Earth dirt and air in the Genesis samples, as expected. But surprisingly, the grit that is proving most problematic for the team at this point isn’t from the crash. “The landing didn’t help,” says Wiens, but “the thing that’s proving most difficult for us happened in flight.” A fine layer of lubricants and other craft-building materials has wound up on the samples, he says. That was expected, he notes, but it is proving tricky to deal with.

Earth contamination can be separated from the samples mainly because the solar wind whacked into the collector at speed, burying sample particles some 40 nanometres deep.

Because dirt and air from Earth contain relatively little neon and argon, the current Science study was not much affected by this type of contamination, says Wiens.

Mission not impossible

Importantly, the team remains hopeful that they will be able to get results on oxygen and nitrogen isotopes from the mission. For this they plan to examine a collecting dish that, although banged up and dirtied by the landing, seems to have succeeded in gathering up enough of these elements for measurement.

Nitrogen is of interest because on the Moon, isotopes of this element vary greatly from one soil sample to another, even though all nitrogen is thought to come from the solar wind. Researchers want to know the reason for this variation.

Oxygen isotopes are even odder, as they seem to have unique ‘fingerprint’ values in different types of objects. “If someone brings a rock into a lab that measures oxygen isotopes we can tell if it’s from Earth or space or the Moon. But we’re still trying to work out why that is,” says Wiens. Knowing the value in the Sun, and hence the early Solar System, is expected to pin down the reason for this oddity.

“It’s still going to be a bit of a struggle, but I’m confident we’ll get oxygen and nitrogen within a couple of years,” says Wiens. "I'm optimistic. It's just taking time," agrees McKeegan. 

  • References

    1. Grimberg, A. , Burnett, D. S. , Bochsler, P. , Baurl, H. & Wielerl, R. Space Sci. Rev. 130, 293-300 (2007).
    2. Wiens, R. C. et al. Space Sci. Rev. 130, 161-171 (2007).
    3. Reisenfeld, D. B. et al. Space Sci. Rev. 130, 79-86 (2007).
    4. Heber, V. S. et al. Space Sci. Rev. 130, 309-316 (2007).
    5. Meshik, A. et al. Science 318, 433-435 (2007).
    6. Grimberg, A. et al. Science 314, 1133-1135 (2006).
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