Jarosite: a pure clock on Mars

Jarosite crystals from Sierra Peña Blanca in Mexico.
| Picture Credit score: Robert M. Lavinsky (CC BY-SA)

Jarosite is a yellow-brown mineral that accommodates potassium, iron, and sulphate — and researchers have discovered it may function a pure geological clock on Mars.

Not too long ago, a staff of researchers from round India sampled six jarosite veins from Kachchh in Gujarat, whose arid, salty terrain is much like that of Mars.

Within the lab, the staff analysed how a lot gentle the mineral emitted because of the vitality it had saved from pure radiation, a phenomenon known as luminescence. First, they washed the grains in weak acid to roughly double their brightness, then zapped them with radiation, heated them, cooled them, and repeated the cycle many occasions.

This manner, they revealed 4 clear emissions at about 100° C, 150° C, 300° C, and 350° C, even after baking the grains to 450 °C. This meant jarosite may survive being heated by a rover’s drill with out dropping its potential to luminesce.

When the staff measured how the glow grew with additional radiation, they discovered the grains turned saturated between 590 and a couple of,600 grey (the SI unit of absorbed radiation dose). On Mars, pure radiation is roughly 65 milligray/12 months, so jarosite can report occasions that occurred throughout the final 25,000 years.

As a result of jarosite is frequent on Mars, robust, and simple to learn with small heaters and LEDs, the researchers have urged future rovers may use it to this point mud storms, historical flood deposits, and volcanic ash.