How old is Mars?
Scientists at the California Institute of Technology have succeeded in establishing the age of a rock from the red planet with a technique similar to that used for dating terrestrial rocks. The results, obtained thanks to the rover Curiosity of NASA, are published in one of the six articles published this week in Science.
Since the mass spectrometer of chlorine -36, potassium -40 from the radiocarbon in the last seventy years dating techniques to determine the age of rocks and ancient objects have been refined more and more. By analyzing the process of decay of various radioactive isotopes has been possible to estimate the age of any material on Earth. But radiocarbon dating has never been pushed out from our planet, and the estimated age of extraterrestrial objects has always been made from what extraterrestrial had available: meteorites, space rocks, and lunar samples. Until now. For the first time in history, it was determined the age of a rock on the planet Mars and the process of dating was done directly on the Martian surface.
Author of the experiment is a research group at the California Institute of Technology (Caltech), led by geochemist Ken Farley. The project was part of a larger design of the Mars Science Laboratory (MSL) in preparation for the Mars mission that began in 2011. Before launching the Curiosity rover to the Red Planet once, in fact, NASA had asked a selection of scientists around the world to propose possible experiments to do with the equipment already designed by the MSL. Farley had proposed to analyze the rocks of Mars using techniques similar to those used for dating terrestrial. The idea was liked, the project started.
Then came the first results, and with them a whole new perspective with which it can be looked at the geologic history of Mars. The rocks which can be studied just as those from Earth: in particular, with the technique potassium – argon. It is a dating method which consists in the measurement of how much argon gas is contained in a rock and in the calculation of the decay time of the element from which the potassium gas has originated. In fact, the atoms of the radioactive isotope of potassium (called potassium -40) decay over time into a rock that spontaneously form stable atoms of argon -40. The decay occurs in a known interval, amounting to 1.3 billion years, and then determining the amount of argon -40 in a rock can be calculated with good approximation its age.
This dating requires sophisticated tools, not easy to carry and to use in space on the surface of other planets. But Farley has circumvented the obstacle thanks to the Sample Analysis on Mars (SAM) of NASA, using the robotic arm of Curiosity that has taken samples of rocks and has “shipped” them to the analysis laboratory located in the heart of the rover. Here the temperatures of Martian rocks have been raised so high as to release the gas and thus to be able to apply the techniques of radiocarbon dating. The verdict: Mars 3.86000000000 to 4.56000000000 years. Or at least one of its rocks: in order to have a complete answer must await further results. This fact, however, is able to confirm the earlier assumptions made by counting craters, estimates based on the simple principle that a planet with more craters has been bombarded by meteorites and is therefore most likely older. That prefigures well for the reliability of the technique used by researchers at Caltech.
“In a sense, this result is not surprising: it is the number that everyone expected,” said Ken Farley. “The amazing thing is that we got it with equipment that was not designed for this purpose. The fact that the data are consistent with previous estimates shows that the technique works, and it works pretty well.”
The results of the study were published this week in Science, along with five other articles that have reported the first stages of the fascinating journey of Curiosity on the Red Planet. Radiometric dating seems so full right to be entered in the set of techniques used for one of the main objectives of the mission, to explore the possibility of life in the ancient past of Mars.