Can life exist in the harsh conditions of our solar system? Could life evolve and survive under the extreme heat and pressure of Venus, under the icy crust of Mars, or in the oceans of Europa? To find out just how resilient life is, scientists have been looking for answers in some of the most hostile environments on Earth. And in recent years, life has been discovered in the most extreme conditions, previously thought to be uninhabitable. These microorganisms are sometimes called extremophiles.

There are many different classes of extremophiles, which are named according to the environmental conditions in which they thrive. For example, a thermophile is an organism which lives in conditions between 60˚ and 80˚ Celsius. Recently, a thermophile was discovered nearly two miles beneath the Earth’s surface in the Mponeng Gold mine of South Africa. This particular discovery is interesting because these thermophiles are completely devoid of sunlight, surviving on the byproducts of radioactive decay.

Where might we look for extremophiles outside of Earth? Mars is a good place to start. With the recent confirmation of ice in the crust, it is possible that water has trickled deep into the Martian interior, where thermophiles can survive off of radioactive materials like previously discussed. On Earth, we have discovered halophiles, which require high amounts of salt to survive; recently, the Phoenix Lander discovered several different types of salts in the Martian soil, which could be another location to search for life. Other types of extremophiles discovered on Earth may also apply to Mars, such as: xerophiles, hypoliths, and radioresistant extremophiles.

Europa is another great place to look for extremophiles. It is theorized that there is a global ocean beneath Europa’s thick layer of surface ice. Sattelite images of Europa’s surface show a complex system of tectonic activity–places where the ice has broken and liquid water has upwelled to the surface and refrozen. This tectonic activity is likely the result of tidal flexing, due to the gravitational pull of Jupiter. This tidal flexing may also produce hydrothermal vents. Earth’s hydrothermal vents are host to a large amount of biological activity, meaning Europa is a very promising place to look for extremophiles.

There are future plans in the works to search for extremophiles in the Martian crust. Astrobiological missions to Europa, Titan, or elsewhere are probably deep into the future. Given the amount of life discovered in the harshest places on Earth, I will be surprised if we find that our solar system is devoid of life.

The most historically observed planet in the solar system, Mars, has been the subject of astronomy since at least 400 B.C. when the Babylonians began making sophisticated predictions of the heavens. Since 1960 there have been 38 attempted missions to Mars, with only 19 successes. This 50% success rate has become known has the Mars Curse.

Perhaps the Mars Curse has been lifted because recent missions have been more successful including 6 of 7 Martian Landers. Included in this figure is Spirit and Opportunity which were launched in June 2003 and designed to last 90 Sols. The Rovers have far surpassed this expectation, with Spirit on Sol 1647, and Opportunity on Sol 1626. The rovers have made several important discoveries, including a patch of nearly pure Silica, which could be a promising place to look for signs of past microbial life. On Earth similar patches of Silica are formed from hot-springs and fumaroles which are both full of microbial life. Also currently on the Martian surface is the Phoenix Lander which has made it share of important discoveries, including: water, clay and several different salts. Water has previously been detected on the Martian surface but this is the first time it has been detected using a direct chemical analysis of the soil.

As knowledge is built, more questions arise, and future missions are being designed to answer such questions. Future mission include the international Mars Science Laboratory which is slated to launch this fall. This Rover will be equipped to determine if organic compounds are present in the soil, and to determine what geological processes may have formed samples of rock. Other future missions may include UAV scout missions, Mars Sample Return, an Astrobiology Field Laboratory, and eventually it will be necessary to send manned missions to Mars.

There is a lot of excitement lately about the wet history of Mars, but what about Venus? Did Venus once have a climate which could support liquid water, if so where is the evidence? There are mountains, volcanoes, rift valleys, impact craters, and two small areas of slightly higher elevation which resemble continents. Any physical evidence of past water on Venus would have been wiped out by geological processes which keep the majority of the Venusian surface relatively young.

The atmosphere on Venus is composed of 96% carbon dioxide, 3% nitrogen, and the remainder (less than 1%) is made up of water vapor, sulfur dioxide, argon, and carbon monoxide. The small amounts of water vapor in the atmosphere plus the high levels of CO2 and thick clouds of sulfuric acid may well have been generated by volcanic activity.

It’s difficult to hypothesize water in substantial quantities when there is less than 1% detected in the Venusian atmosphere. Recently, Venus Express observed H+, O+, and He+ ions escaping the Venusian atmosphere. This finding could suggest that the water vapor has been stripped apart by ionizing forces such as solar radiation or electro magnetic activity over billions of years. Hydroxyl was also recently discovered (for the first time on another planet) by Venus Express. Hydroxyl is closely linked to ozone, which could potentially protect a planet from solar radiation and slow the breakup of water vapor.

So what did happen to Venus? Was it at one time more Earth-like with oceans, rivers, and lakes whose evidence was all erased by volcanic activity, or by some external catastrophic event which also put the planet into a retrograde rotation? Was all of this alleged water evaporated into space and then subsequently broken into constituent ions which then escaped into space leaving massive quantities of CO2? Or rather is the premise that there was once a large amount of water inherently wrong? Perhaps there never was water on the surface of Venus and perhaps the dense atmosphere was formed primarily by volcanic activity. One thing is certain; to conclude that Venus was previously water bearing will require further exploration into the planet’s past.