Publication Date:
1997-03-14
Description:
Indirect evidence for life on Mars has been reported from the study of meteorite ALH84001. The formation temperature of the carbonates is controversial; some estimates suggest 20 degrees to 80 degrees C, whereas others exceed 650 degrees C. Paleomagnetism can be used to distinguish between these possibilities because heating can remagnetize ferrimagnetic minerals. Study of two adjacent pyroxene grains from the crushed zone of ALH84001 shows that each possesses a stable natural remanent magnetization (NRM), implying that Mars had a substantial magnetic field when the grains cooled. However, NRM directions from these particles differ, implying that the meteorite has not been heated significantly since the formation of the internal crushed zone about 4 billion years ago. The carbonate globules postdate this brecciation, and thus formed at low temperatures.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Kirschvink, J L -- Maine, A T -- Vali, H -- New York, N.Y. -- Science. 1997 Mar 14;275(5306):1629-33.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Division of Geological and Planetary Sciences, California Institute of Technology, 170-25, Pasadena, CA 91125, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/9054354" target="_blank"〉PubMed〈/a〉
Keywords:
Carbonates/*chemistry
;
Magnetics
;
*Mars
;
*Meteoroids
;
Minerals/*chemistry
;
Temperature
Print ISSN:
0036-8075
Electronic ISSN:
1095-9203
Topics:
Biology
,
Chemistry and Pharmacology
,
Computer Science
,
Medicine
,
Natural Sciences in General
,
Physics
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