Curiosity sitting on Martian rocks akin to those in Mexico

Millions of years ago fire and water forged the gypsum rocks locked in marshes of Cuatro Cienegas, a Mexican valley similar to Gale crater on Mars.

"Cuatro Cienegas is extraordinarily similar to Mars. As well as the Gale crater where Curiosity is currently located on its exploration of the Red planet, this landscape is the home to gypsum formed by fire beneath the seabed," said Valeria Souza, evolutionary ecologist at the National Autonomous University of Mexico (UNAM).

Souza explained that sulphur components from magma and minerals from the sea (carbonates and molecules with magnesium) are required to form gypsum.

In the case of the Cuatro Cienegas Basin, the magma under the seabed was very active. In fact, it allowed for the continent displacement during the Jurassic Period.

"Here was where the supercontinent Pangea opened up some 200 million years ago, pushing the hemisphere north from the equator where it is now," Souza said in a statement.

In the case of Mars, scientists have not been able to confirm tectonic movement in its crust at any point, but they believe that a large meteorite crashed into its primitive sea.

The fact that probing has detected gypsum in the Gale crater indicates that mineral-rich water was present and that sulphur was able to form due to the impact of the meteorite causing the crater.

It is no easy task to find a place on Earth similar to this Martian environment, except in Cuatro Cienegas. So astrobiologists toiled to understand how its bacterial communities work.

"This oasis in the middle of the Chihuahua desert is a time machine for organisms that, together as a community, have transformed our blue planet yet have survived all extinctions. How they have managed to do this can be revealed by their genes," Souza said.

The team have analysed the 'metagenomes', the genome of the different bacterial communities that proliferate in these marshes by adapting parallel strategies to overcome survival challenges in a place with so little nutrients.

The results published in the journal Astrobiology reflect the existence of two communities in different pits. One is 'green' and is formed by cyanobacteria and proteobacteria that have adapted to the lack of nitrogen.

Another is 'red' and is made of Pseudomonas and other micro-organisms that live without phosphorus. There are also blue springs which are generally deeper and lacking in nutrients.

"Understanding the usage and exploitation strategies of phosphorus is necessary in understanding what could happen in extreme scenarios like on other planets where there is a possibly serious limitation to this and other nutrients," said researcher Luis David Alcaraz.