Using neutron and X-ray tomography, a team of planetary researchers from Lund University and elsewhere examined a section of Miller Range (MIL) 03346, a nakhlite meteorite from Miller Range in Antarctica.
Nakhlites are a group of igneous Martian meteorites that are rich in minerals called pyroxene and olivine.
One key finding in these meteorites is evidence for preterrestrial, Martian, aqueous alteration of olivine grains.
All nakhlites found to date are thought to derive from the same volcanic system, on the basis of their similar petrology, geochemistry, and ejection age of 11 million years.
The nakhlites were emplaced in at least four magmatic events, with crystallization ages ranging from 1.42 to 1.32 billion years ago.
Suggested source locations are the large volcanic terrain of the Northern Plains, Tharsis, Elysium-Amazonis volcanic plains, and Syrtis Major.
“Since water is central to the question of whether life ever existed on Mars, we wanted to investigate how much of the MIL 03346 nakhlite meteorite reacted with water when it was still part of the Mars bedrock,” said Josefin Martell, a doctoral student at Lund University.
To answer the question of whether there was any major hydrothermal system, which is generally a favorable environment for life to occur, Martell and colleagues used neutron and X-ray tomography.
X-ray tomography is a common method of examining an object without damaging it. Neutron tomography was used because neutrons are very sensitive to hydrogen.
This means that if a mineral contains hydrogen, it is possible to study it in three dimensions and see where in the meteorite the hydrogen is located.
Hydrogen is always of interest when scientists study material from Mars, because water is a prerequisite for life as we know it.
The results show that a fairly small part of the sample seems to have reacted with water, and that it therefore probably wasn’t a large hydrothermal system that gave rise to the alteration.
“A more probable explanation is that the reaction took place after small accumulations of underground ice melted during a meteorite impact about 630 million years ago,” Martell said.
“Of course, that doesn’t mean that life couldn’t have existed in other places on Mars, or that there couldn’t have been life at other times.”
The findings appear in the journal Science Advances.
Josefin Martell et al. 2022. The scale of a Martian hydrothermal system explored using combined neutron and X-ray tomography. Science Advances 8 (19); doi: 10.1126/sciadv.abn3044