| | PSRD: ALH 84001 magnetite (Site not responding. Last check: 2007-07-20) |
 | | The magnetite grains reside in tiny grains of iron-magnesium-calcium carbonates, which are typically 50-200 micrometers across and are dispersed throughout the ALH 84001 meteorite as disk-shaped or spheroidal grains, or, in the case of carbonates that enclose silicate fragments, as irregularly shaped grains. |
 | | Although all workers agree that the magnetites in ALH 84001 were formed on Mars and may contain an important record of an ancient Martian magnetic field, many have argued against a biological origin for the magnetites. |
 | | Since we found much evidence for localized shock melting of silicate minerals in ALH 84001, and there is additional evidence that the rock was heated by impact 4 Byr ago, it is probable that the carbonate was decomposed by impact heating, at this time, rather than by deep burial in the planet. |
| www.psrd.hawaii.edu /May02/ALH84001magnetite.html (3575 words) |