Snows of yesteryear
Do ice meteorites exist? And how can we find them if they do? Joe McCall investigates…
If we accept the chemical condensation model of the Solar System
1,2 ice meteorites should exist. But they would melt on impact, in any temperature zone except Antarctica, where they could be recovered
3. But how could we distinguish them from terrestrial ice? Such ‘dirty ice balls’ could be detected by studying their radioactive isotope content or organic chemicals. Acoustic and electromagnetic techniques (using long wavelengths, 10-40Hz) are likely to be useful and one would need a refrigerated transport system.
Hegyi et al.
4 suggest using a Husar rover, equipped with suitable instruments. Ammonia and methane, they suggest, may be the clue to detection. They would drill to 3cm and place a gas sensor in the hole. Conductivity would be measured. Any sample would be recovered using a robotic arm, and GPS would position the recovery site precisely. They envisage three rovers working in parallel to cover a large area.
Fodor
3 envisages extending the search to the Moon, ‘using the perpendicular
suspended LIDAR technique on the well known optical package which works as laser optical localisators’. This is an entirely new proposition and covers untried
methods. Scientists in China recovered in 1995 what they believed to be chunks of meteoritic ice which ‘plummeted to Earth’ in Zhejiang Province (just south of Shanghai)5. An amateur geologist, Zhong Gongpei, was nearby when farmers saw three large chunks of ice crash into paddy fields of Yaodou village. A cloudy streak and a ‘whooing sound’ were reported, before they crashed down in three fields one kilometre apart. One fist-sized piece left a crater one metre in diameter. A frozen food company kept them from melting. Meteorite expert Wang Sichao of the Purple Mountain Observatory, Jiangsu Province, said that they were probably ice meteorites, but further analysis was needed to confirm this, including analysis for isotopes and cosmic dust. The ice was apparently white, transparent, of irregular shape with air bubbles (?) on the surface and within. It was light and did not show the familiar layered structure of hailstones.
Was this a tall story? No mention of the analytical results is available 13 years later, and one must assume that the results were negative. One alternative possibility is that the lumps fell off the wing of an aircraft. There is also the question of friction in atmospheric entry. Ice meteorites would be likely to melt much further in - or entirely - on atmospheric entry: perhaps only quite large ice bodies would survive to land, even in Antarctica.
It is apparent that interest in ice meteorites has been revived and there will be searches in Antarctica and on the Moon, in the near future backed up my ‘state of the art’ technology. Mars, however, is too dusty to be a suitable location for such research3.
References
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- Bérczi, Sz, Lukács, B 1994 Icy meteorites on Antarctica 19th NIPR Symposium on Antarctic meteorites, p 19.
- Földi, T, Bérczi, Sz, Lukács, B 1995 Search for icy meteorites in Antractica. 20th NIPR Symposium on Antarctic meteorites, p68.
- Fodor, E 2008 Technological methods in the search for icy meteorites on cold regions. Meteoritics and Planetary Science 43 Supplement, A181.
- Hegyi, S, Kovács, B, Hudoba, Gy, Istenes, Z, Bérczi, Sz 2008. Search for ice meteorite in Antacrtica by Husar Rover. Meteoritics and Planetary Science 43 Supplement, A183.
- http://www2.jpl.nasa.gov/s19/news56.html : (1995 report by J Parker)