Humans have not yet set foot on Mars, but as time passes, Mars has come to humans. Chunks of Martian rock, ejected from their homeworld by processes such as violent impacts, eventually made their way through the solar system. – Collision with Earth.
When collecting these samples from our neighboring planet, a strange pattern emerged. Most of the samples appear to be rocks that formed fairly recently on the Red Planet. This is unusual given that much of Mars’ surface is very old.
Age measurements can be seriously wrong. Different dating techniques give different results, meaning scientists are not completely confident in estimating when these rocks formed on Mars.
A team of scientists from the US and UK has discovered a way to solve this problem. And surprisingly, many of these rocks are actually very young, only hundreds of millions of years old. This information could provide clues about how long it took for the meteorite to get here and about Mars’ geological processes.
“Certain chemical signatures indicate that these meteorites are definitely of Mars origin.” says volcanologist Ben Cohen. from the University of Glasgow, who led the research.
“They were blown off the Red Planet by a massive impact and formed large craters. But Mars has tens of thousands of impact craters, so we don’t know exactly where on Earth the meteorites came from. .The best clue we can use to identify the source crater is the age of the sample.”
Approximately 360 meteorite samples have been discovered on Earth and identified as originating from Mars.Several 302 of them As of this writing, that is, most of them are categorized as: shergottitea type of metal-rich Martian stone forged in the heat of volcanic activity.
Based on the abundance of craters on Mars’ surface, scientists estimate that its surface is quite old. If the Earth’s surface is young and renewed by volcanic activity, many craters will be obliterated by volcanic flows. Therefore, rocks ejected from the surface of Mars must also be old.
Dating shergottite here on Earth is complicated not only by its composition, but also by the very little information we have been able to glean from it, suggesting that much of it is less than 200 million years old. I am. This gave rise to a phenomenon known as the shergottite-age paradox. They’ve been eavesdropping on scientists for decades..
An explanation for this surprisingly young possibility is that all the young shergottites may have come from a single origin, but were fractured to such an extent that an impact event heated the rock and reset its age. My thoughts were wide-ranging. However, these theories did not match the evidence – the rock itself.
The method used to determine the age of shergottites is known as: argon-argon dating, which is based on the decay of radioactive potassium into argon. This rate of decay produces a known ratio of argon isotopes that scientists can examine to determine how long radioactive decay has occurred and determine the age of a rock sample.
The problem is that here on Earth, we can easily account for the many different sources of argon that can get into our samples. Shergottites originated on a completely different planet and we know how long they were in space, but this is more complicated. Shergottite has five potential sources of argon, while Earth’s rocks only have three.
To compensate for this, Cohen and his colleagues have developed a method to correct for argon pollution from Earth and space. “When we did that, we found that the argon-argon age was young and perfectly consistent with other methods such as uranium-lead.” he explains.
They dated seven samples of shergottite, with ages ranging from 161 million to 540 million years ago. Researchers say the reason for this may be that frequent impacts to Mars destroyed the old surface, exposing younger rocks beneath, which were replenished by volcanic activity. Eventually, younger rock is more likely to be excavated and ejected.
Volcanic activity on Mars may still be ongoing, and Mars is under constant bombardment.Scientists have made some estimates 200 impacts per year A crater over 4 meters in diameter is created. So it’s probably no surprise that young rocks are occasionally hurled toward Earth in detours like our solar system.
This study Earth and Planetary Science Letters.