Scientists discover true age of meteor
The UH Department of Earth and Atmospheric Sciences, in collaboration with NASA, has made recent discoveries that mark the oldest and most well known Martian meteorite as younger than previously presumed.
After 15 months of continuous study of meteorite ALH84001, assistant professor of Geology and Isotope Geochemistry, Thomas Lapen and his team determined that the meteor’s robust age is exactly 4.091 billion years old, which varies significantly from the originally accepted age of 4.5 billion years old.
“The age of this particular meteorite, which has been quoted in literature as being 4.5 billion years old, has never been published before,” Lapen said. “We figured that we could apply a fairly new system, lutetium-hafnium isotope analysis, and calculate a robust age for the stone.”
The discovery helped Lapen and his team better understand Mars’ volcanic activity, as well as how it compares to younger meteorites.
“These meteorites come from volcanoes on Mars, and when comparing (ALH84001) to a meteor that is 500-150 million years old, it appears that the sources of the magma that produced the very old rock are very similar to those that produced the young rock,” Lapen said. “We can then infer that the volcanic processes occurring in Mars have been occurring in the same way for most of Mars’ history.”
The sample that was used in the study was provided to Lapen and his team, which included former NASA scientist and UH associate professor of Isotope Geochemistry Alan Brandon and two post-doctoral researchers, Minako Righter and John Shafer, from the NASA Antarctic meteorite curator and the Meteorite Working Group.
ALH84001 was found in 1984 in the Allan Hills of Antarctica and is the only meteorite sample scientists have from Mars’ early history.
Its age is roughly more than 2.5 billion years older than any other available sample. Due to this, any results found from the study of this sample help scientists better understand the relationship between planets, especially Earth and Mars.
“These results put a context for how we think of Mars in terms of its evolution and planet evolution in general,” Lapen said. “Our data suggests that while Earth is dynamic because of its plate tectonics and how it is constantly recycling materials from its crust into the mantel, Mars remains in a steady state for most of its existence.”
Future analysis and subsequent studies will help reveal the full implications of what this means in terms of evolution really means.
“The rock crystallized around the same time Mars was suitable for life, and only future analysis will be able to tell,” Lapen said. “Our findings don’t preclude there being evidence for life on Mars but at the same time doesn’t say there is evidence.”
The findings were published in an article, titled “A Younger Age for ALH84001 and Its Geochemical Link to Shergottite Sources in Mars,” in the April 16 issue of Science, an international weekly journal, which is self-proclaimed as “the world’s leading outlet for scientific news, commentary, and cutting-edge research” on its Web site.