Martian rocks are proven to have made their way to Earth. As scientists collect those chunks, they noticed an emerging pattern of recent formation, challenging dating methods.
Scientists from the US and the UK have addressed this issue, determining that many of these rocks are relatively young, offering insights into their journey and Martian geology. These meteorites, with distinct Martian characteristics, were ejected by massive impact events, though pinpointing their source crater relies on dating the samples' age.
Martian Rocks on Earth Are Indeed Young
In the study published in Earth and Planetary Science Letters, researchers showed that many Martian rock samples found on Earth appear relatively young, which contradicts the prevailing notion of Mars having an ancient surface. Inconsistencies in age measurements, resulting from various dating techniques, have created uncertainty regarding the rocks' formation periods.
The majority of the meteorite samples of Martian origin, approximately 302 out of 360 known samples, are classified as shergottites, a type of Mars rock formed through volcanic activity.
Wirh the extensive cratering on the Martian surface, it had been assumed that the surface was ancient. If the surface were younger due to volcanic activity, many craters would have been erased by lava flows, suggesting that ejected Martian rocks should also be old.
However, dating shergottites on Earth are complicated due to their composition. Surprisingly, the limited dating data available for these rocks indicates that many of them are less than 200 million years old, leading to the shergottite age paradox, which has puzzled scientists for years.
READ ALSO: NASA's Perseverance Rover Collected Martian Lava Rocks Altered by Water in Jezero Crater
Determining the Age of Martian Rock Samples
Martian meteorites have traditionally been dated using various methods, yielding a range of ages. One such technique is the "argon-argon" method, which measures the decay of potassium-40 to argon-40.
While this method is versatile for dating Earth rocks, it becomes more complex for meteorites that have traveled through space for extended periods. Shergottite meteorites, in particular, present challenges due to the presence of additional argon sources compared to Earth rocks.
To address these challenges, researchers led by University of Glasgow volcanologist Ben Cohen utilized modern equipment and technology to reevaluate seven Martian meteorites.
They employed a research-only nuclear reactor to precisely measure argon concentrations in the meteorites and correct for any contamination from both the Martian and Earth atmospheres. The refined argon-argon dating method provided ages that aligned with other dating methods, such as Uranium-Lead.
Researchers explored hypotheses to address the Shergottite Age Paradox but found that these ideas did not match the rock evidence. After conducting age dating on seven shergottite samples, they determined ages ranging from 161 million to 540 million years ago.
They propose that Mars' continuous bombardment has disrupted its older surface, exposing and rejuvenating younger rocks beneath, making it more likely for younger layers to be excavated and ejected. Ongoing Martian volcanic activity and frequent impacts (about 200 per year creating craters over 4 meters in diameter) contribute to the ejection of younger Martian rocks toward Earth.
RELATED ARTICLE: How Did Fragments of Mars Reach Earth? Astronomers Explain the Complex Process of the Origin of These Martian Rocks
Check out more news and information on Space in Science Times.
