Posted on by Jerry Coffey

Is There Life On Other Planets

Temperature of Mars
What is the Temperature of Mars? Image credit: NASA/JPL

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Is there life on other planets? That has been a question raised from the early beginnings of science fiction. The notion was scoffed at as pure mind play for dreamers and the occasional grifter selling rides to the Moon. At least it was until we were able to reach into space and discover new facts and gather new intel.

The possibility of life on Mars(outside sci-fi books) had been proposed as early as the 1950’s, but there was no real way to prove or disprove the theory until the launch of Mariner 4 in 1965. The spacecraft was able to return the first photographs of the planet’s surface. The news was all bad for those who had hoped for signs of life on the planet. The surface was too extreme and desolate for any type of known life form. The Voyager probes found radiolabeled carbon dioxide, but no organic molecules. Those results give mixed signals and are inconclusive at best. The results have been used to support the possibility of a microorganism named Gillevinia straata.

The Phoenix lander touched down on the Martian surface in May of 2008. The lander dug a trench on the area of the northern pole. No bacteria was found but the samples did contain bound water and carbon dioxide. The most positive evidence of life in the Martian past are meteorites from the planet. 34 exist and 3 show signs of microscopic fossilized bacteria.

Another viable possibility for life on other planets would be those similar to Gliese 581c. These planets are within the habitable zone(for human life) of their main sequence star. These planets appear to have a temperature that would allow liquid water and atmosphere’s that seem spectroscopically close to Earth’s. The information that is needed would detail the greenhouse effect on these planets. If that was available, we would be able to determine suitability for human life.

All of our efforts to answer the question ‘Is there life on other planets?’ are based on finding life that is similar to that on Earth. That is a typically arrogant line of research. Where is it written that the Earth type of life form is pervasive?

We have written many articles about the possibility of life on other planets for Universe Today. Here’s an article about the life on other planets, and here’s an article about life on Mars.

If you’d like more info on the search for life on other planets, check out the NASA Astrobiology Institute Homepage, and here’s a link to NASA Planet Quest: Finding Life.

We’ve also recorded an entire episode of Astronomy Cast all about the Future of Astronomy. Listen here, Episode 188: The Future of Astronomy.

Posted on by Jean Tate

Exobiology

Exobiology (same thing as astrobiology) is about life in space (on other planets, and moons; in other solar systems): where it is, what it is, how it started, and how it evolved (all studied scientifically, of course). Because the origin of life right here on Earth, and its early evolution, is essentially unknown, and because of the distinct possibility of similiarities with the origin (and early evolution) of life elsewhere in the universe, exobiology includes research into abiogenesis (and early, and extreme, life on Earth).

Exobiology is very much a multi-disciplinary field, drawing on biology, chemistry, geology (and planetary science), physics, and astronomy.

Because we have a sample of just one – life on Earth – it is difficult to make anything but the most general decisions on what lines of exobiology research are likely to be productive (keep in mind that null results can, of course, be quite productive). Conservatively, looking for planets like Earth in orbit around stars like the Sun (in age as well as mass, metallicity, etc), and looking for clues for fossil life in planetary environments like those found today on Earth (e.g. early Mars) seem better options than investigating possible silicon-based life (to take just one example).

As the number of exosolar (or extrasolar) planetary systems known continues to grow, quickly, discovering the prevalence of Earth-mass planets, in goldilocks orbital zones, seems like a good idea … so today we have the Kepler mission and COROT.

As the early Mars becomes better understood – and the widespread distribution of liquid water then – so today we have plans for the Mars Science Laboratory and ExoMars (the discovery of methane in the Martian atmosphere certainly spurs such developments).

Less conservatively, the discovery of life around black smokers and sites like Lost City (not to mention entire ecosystems within crustal rocks … several km beneath the surface) sparked interest in the possibility of life in Europa, on Titan, even Enceladus (life – albeit rather simple life – we now know does not need to depend, ultimately, on the Sun’s (or another star’s) radiant energy … think chemolithoautotrophs).

Did you know that NASA has an exobiology branch? Check it out! Duke University’s Chemistry Department has an interesting Introduction to Exobiology you might find interesting too.

Universe Today stories on exobiology? Yep, lots; here’s a random selection: Martian Explorers Should Be Looking for Fossils, Did Life Arrive Before the Solar System Even Formed?, Extremophile Hunt Begins in Antarctica, Implications for Exobiologists , and New Targets to Search for Life on Europa.

Any Astronomy Cast episodes on exobiology? Yep … but it’s called Astrobiology.

Sources: NASA, ESA

Posted on by Nicholos Wethington

Bacteria Could Survive in Martian Soil

Certain strains of bacteria, including Bacilus Pumilus, may be able to survive on the Martian surface. Image credit: NASA

Multiple missions have been sent to Mars with the hopes of testing the surface of the planet for life – or the conditions that could create life – on the Red Planet. The question of whether life in the form of bacteria (or something even more exotic!) exists on Mars is hotly debated, and still requires a resolute yes or no. Experiments done right here on Earth that simulate the conditions on Mars and their effects on terrestrial bacteria show that it is entirely possible for certain strains of bacteria to weather the harsh environment of Mars.

A team led by Giuseppe Galletta of the Department of Astronomy at the University of Padova simulated the conditions present on Mars, and then introduced several strains of bacteria into the simulator to record their survival rate. The simulator – named LISA (Laboratorio Italiano Simulazione Ambienti) – reproduced surface conditions on Mars, with temperatures ranging from +23 to -80 degrees Celsius (73 to -112 Fahrenheit), a 95% CO2 atmosphere at low pressures of 6 to 9 millibars, and very strong ultraviolet radiation. The results – some of the strains of bacteria were shown to survive up to 28 hours under these conditions, an amazing feat given that there is nowhere on the surface of the Earth where the temperatures get this low or the ultraviolet radiation is as strong as on Mars.

Two of the strains of bacteria tested – Bacillus pumilus and Bacillus Nealsonii – are both commonly used in laboratory tests of extreme environmental factors and their effects on bacteria because of their ability to produce endospores when stressed. Endospores are internal structures of the bacteria that encapsulate the DNA and part of the cytoplasm in a thick wall, to prevent the DNA from being damaged.

Galletta’s team found that the vegetative cells of the bacteria died after only a few minutes, due to the low water content and high UV radiation. The endospores, however, were able to survive between 4 and 28 hours, even when exposed directly to the UV light. The researchers simulated the dusty surface of Mars by blowing volcanic ash or dust of red iron oxide on the samples. When covered with the dust, the samples showed an even higher percentage of survival, meaning that it’s possible for a hardy bacterial strain to survive underneath the surface of the soil for very long periods of time. The deeper underneath the soil an organism is, the more hospitable the conditions become; water content increases, and the UV radiation is absorbed from the soil above.

Given these findings, and all of the rich data that came in last year from the Phoenix lander – especially the discovery of perchlorates –  continuing the search for life on Mars still seems a plausible endeavor.

Though this surely isn’t a confirmation of life on Mars, it shows that even life that isn’t adapted to the conditions of the planet could potentially hold out against the extreme nature of the environment there, and bodes well for the possibility of Martian bacterial life forms. The LISA simulations also indicate the importance of avoiding cross-contamination of bacteria from Earth to Mars on any scientific missions that travel to the planet. In other words, when we finally are able to definitively test for life on our neighboring planet, we don’t want to find out that our Earth bacteria have killed off all the native lifeforms!

Sources: Arxiv papers here and here.