SOLID Clues for Finding Life on Mars


Researchers from the Center of Astrobiology (CAB) in Spain and the Catholic University of the North in Chile have found an “oasis” of microorganisms living two meters beneath the arid soil of the Atacama, proving that even on the driest place on Earth, life finds a way.

Chile’s Atacama Desert receives on average less than .01 cm (.004 inches) of rain per year. In some locations rain has not fallen for over 400 years. But even in this harsh environment there is moisture… just enough, at least, for rock salts and other compounds that can absorb any traces of water to support microbial life beneath the surface.

Using a device called SOLID (Signs Of LIfe Detection) developed by CAB, the researchers were able to identify the presence of microorganisms living on thin films of water within the salty subsurface soil.

Even the substrate itself is able to absorb moisture from the air, concentrating it into films only a few microns thick around the salt crystals. This gives the microorganisms everything they need to survive and flourish — two to three meters underground.

SOLID's array of life-detector modules. (CAB)

At that depth, there is no sunlight and no oxygen, but there is life.

And even when researchers dug to a depth of five meters (a little over 16 feet) and took samples back to a lab, they were able to not only locate microorganisms but also revive them with the addition of a little water.

Of course, the implications for finding life — or at least the remains of its past existence — on Mars is evident. Mars has been shown to have saline deposits in many regions, and the salt is what helps water remain liquid, longer.

“The high concentration of salt has a double effect: it absorbs water between the crystals and lowers the freezing point, so that they can have thin films of water (in brine) at temperatures several degrees below zero, up to minus 20 C,” said Victor Parro, researcher from the Center of Astrobiology (INTA-CSIC, Spain) and coordinator of the study. This is within the temperature range of many regions of Mars, and also anything located several meters below the surface would be well protected from UV radiation from the Sun.

“If there are similar microbes on Mars or remains in similar conditions to the ones we have found in Atacama, we could detect them with instruments like SOLID,” Parro said.

The development of a new version of the SOLID instrument is currently underway for ESA’s ExoMars program.

Read more here on the Science Codex article.

What might be found just a few feet under the surface of Mars? (NASA/JPL-Caltech)

States of Matter

Solid, liquid, gas … those are the states of matter we’re thoroughly familiar with, but what makes for a state of matter? And are there other states of matter?

Since people first made distinctions between them, the states of matter were defined by how the matter behaved, in bulk; so a solid had a fixed shape (and volume), a liquid a fixed volume (but changed shape to fit the container it was in), and a gas expanded to fill its container. Once we realized that matter is made up of atoms (and molecules), the states of matter were distinguished by how the molecules (or atoms, in an element) behaved: in solids they are both close by and in a fixed arrangement (e.g. in crystals), in liquids close by but the arrangement is not fixed, and in gases not close by (so no particular arrangement).

But what about plasma? Sorta like a gas – so as it fills any container it’s in, it’s a gas – but not (the ions and electrons interact in completely different ways, in a plasma, than molecules (or atoms) do in a solid, liquid, or gas). Hence, plasma is the fourth state of matter.

Things got a bit more complicated as scientists studied matter more carefully.

For example, if you heat water in a strong, but transparent, container, above a certain temperature (and pressure) – called the critical temperature (critical pressure) – the liquid and gas states become one … the water is now a supercritical fluid (you may have seen this demonstrated, in a chemistry class perhaps, though likely not with water!).

Then there’s the distinction between crystals (crystalline state) and glasses (glassy state); both seem very solid, but the arrangement of molecules in a glass is more like that of molecules in a liquid than those in a crystal … and glasses can flow, just like liquids, if left for a long enough time.

Is there a ‘fifth state of matter’? Yes! A Bose-Einstein condensate (BEC) … which is like a gas, except that the constituent atoms are all (or mostly) in the lowest possible quantum state … so a BEC has bulk properties quite unlike those of any other state of matter (quantum behavior become macroscopic).

In astrophysics, there are quite a few exotic states of matter; for example, in white dwarf stars matter is prevented from further (gravitational) collapse by electron degeneracy pressure; the same sort of thing happens in neutron stars, except that its neutron degeneracy pressure (there may also be an even more extreme state of matter, held up by quark degeneracy pressure!). There’s also a counterpart to ordinary plasmas: quark-gluon plasma (in an ordinary plasma made of hydrogen the atoms are broken into electrons and protons; in a quark-gluon plasma protons and neutrons ‘melt’ into their constituent quarks and gluons).

Are there related Universe Today stories? Sure! For example: Forget Neutron Stars, Quark Stars May Be the Densest Bodies in the Universe, Schwarzschild Radius, and Next Generation Magnetoplasma Rocket Could be Tested on Space Station.

States of matter, including some exotic ones, is something you’ll find discussed in Astronomy Cast; for example this Questions Show.

Purdue University
New York University
Wikipedia: Bose-Einstein Condensate