Did life first arise on Mars?
(appeared in Sep 2017)

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NASA’s Mars rover, Curiosity has found the element, boron on the surface of Mars, says S.Ananthanarayanan.

Boron is an element considered to be essential for life forms to arise. That the planet, Mars, had boron had been inferred from traces found in meteorites that originated in Mars. Taken with other conditions on Mars, this suggested that Mars may have been the source of life on Earth itself. Discovery of boron on the surface of Mars strengthens the possibility.

Patrick J. Gasda, Ethan B. Haldeman, Roger C. Wiens, William Rapin, Thomas F. Bristow, John C. Bridges, Susanne P. Schwenzer, Benton Clark, Kenneth Herkenhoff, Jens Frydenvang, Nina L. Lanza, Sylvestre Maurice, Samuel Clegg, Dorothea M. Delapp, Veronica L. Sanford, Madeleine R. Bodine, and Rhonda McInroy, a team largely at the Los Alamos Lab in New Mexico, with others labs in the USA, Copenhagen and Paris report in the American Geophysical Union journal, Geophysical Letters, the first discovery of boron in rock fissures in the Gale crater region of Mars. The discovery was made by the Martian rover, Curiosity, which deploys ChemCam, the Chemistry and Camera equipment, built at the Los Alamos and the French CESR Laboratories. The rover, a motor car sized vehicle equipped with locomotion, drills, lasers and laboratory capability, has been active on the surface of Mars since August 2012.

A major objective of Curiosity was to see if conditions that support life could have existed on Mars. Initial discoveries by Curiosity included a number of chemical constituents, carbon, hydrogen, nitrogen, oxygen, phosphorus, and Sulphur, the raw materials of amino acids and proteins. This, with the evidence that Mars had abundant water, strongly suggested the possibility of Mars having supported life.

A difficulty in coming finally to this conclusion, however, is that it takes just a little more than the basic building blocks for life forms to arise. This little more is in the form of trace elements, particularly molybdenum and boron, which have to be there for life supporting molecules to be stable. Protein synthesis depends on transcription of pieces of genetic code, which is carried out by DNA-like structures called RNA. Simply putting the correct raw materials is not good enough to form RNA and DNA. Exposing just the raw materials to heat and light would form not RNA but something like tar, Prof Stephen Benner, of the Westheimer Institute for Science and Technology had written in 2013.

Prof Benner noted that just before Curiosity landed on Mars, a large meteorite that originated from a meteor strike on Mars had crashed into the Earth in the Moroccan desert. Analysis of the meteorite showed traces of boron, which suggested that there was boron on Mars. Prof Benner observed that although the Earth had all the necessary ingredients for life to arise, the early Earth was covered with water, while boron only occurs in the driest of places. The early Earth was also oxygen deficient and molybdenum would not have been in the highly-oxidized form that was required.

For these and other reasons, Prof Benner argued that it was not really possible for life to have originated on the earth. On Mars, on the other hand, water did not cover the whole planet and there was evidence that Mars contained the oxidized form of molybdenum. Now with the discovery of boron, Prof Benner suggested that life really originated on Mars and was carried to the Earth perhaps on a piece of rock. While life could not continue on Mars when conditions changed, the changes were for the better on the Earth and here, life has thrived.

This is an attractive theory of the dynamics of the origins of life, early interplanetary travel and reviving the image of the little green men on Mars. The trouble is that the theory is pinned on the presence of boron on Mars and the only evidence we have of this are the traces found on the meteorite of 2011.

Curiosity finds boron

The picture changes with the discovery that the Los Alamos group has announced. The authors of the paper in Geophysical Letters note that the spectral signature of boron has not appeared in remote sensing observations of Mars. CheMin, the Chemistry and Minerology instrument on the Curiosity rover, which uses X Ray scattering and fluorescence to identify elements or minerals in Mars samples, has also not found any traces of boron. The discovery of boron by ChemCam is hence the first time that boron has directly been detected on the surface of Mars.

ChemCam consists of a pair of systems. One has a laser that vaporises and induces the components of rock to emit radiation, which is analyzed by a spectrometer. The presence of elements and compounds can then be detected with great sensitivity. The other system on ChemCam is the high-resolution telescope that provides scientists with images of the sampling areas of rock and soil before and after the laser and spectrometer system zaps them for analysis.

The result of the prospecting has been that boron was detected in a sizeable number of calcium sulphate filled fractures, called ‘veins’, in the rock. The reason for boron not being detected in the rock itself is that the rock has high iron content, and the emission spectrum of iron interferes with that of boron. The presence of boron, in the oxidised form of borate, in the veins suggests that that the boron was came into the veins by the action of water, the paper says. Although the iron content of the rock precludes measurement of boron in the rock, it may well be present, the authors say.

“The presence of boron on Mars opens up new possibilities for habitability because of the important role borate may have played in prebiotic chemistry on early Earth……. Thus, the discovery of boron in Gale crater opens up intriguing questions about whether life could have arisen on Mars,” the paper says. Analysis of the age of borate bearing media would place the earliest and latest time limits on when life could have formed on Mars, the paper says. While some deposits on Mars are of greater antiquity than those on the Earth, study of the Martian geology and the hydrology and the search for borates have become a high priority for Curiosity and future missions to Mars, the paper says.


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