This artist’s impression shows a sunset (speculated and hypothetical) as seen from an exoplanet in another solar system – super-Earth Gliese 667 Cc, in a triple star system. Image Credit: ESO/L. Calçada. Source: http://www.eso.org/public/images/eso1214a/.
While candidates beckon even within our Solar System (particularly moons of other planets), so do the stars at night … and their potential planets and moons.
In this last regard, evidence continues to mount that some such star systems do indeed include planets (known as exoplanets), and that some of those planets host natural satellites, or moons (known as exomoons).
While there are many factors speculated to potentially influence planet and moon habitability, some key ones boil down to an assessment of the presence, or likely presence, of stable liquid water, the availability of energy accessible for life, and likely presence or potential formation of organic compounds.
An Artist’s hypothetical impression of suspected exoplanet Gliese 667 Cb with the the stars Gliese 667 A and Gliese 667 B in the background. Source: http://www.eso.org/public/images/eso0939a/, Image Credit: Credit: ESO/L. Calçada.
Image: public domain, http://mars.nasa.gov/mer/gallery/press/spirit/20050420a.html
The above strikingly detailed image shows a region of Mars called
Artist’s concept of a Mars Rover, public domain image, http://photojournal.jpl.nasa.gov/catalog/PIA04413
Gusev Crater. It was taken by the Mars Spirit rover in 2005.
Mars, today, can be described as appearing similar to a harsh desert on Earth. It is indeed mostly void of liquid water – essential to all life as known on Earth.
Yet, abundant evidence, including present-day Martian landforms, strongly suggests that, during some times in its extremely ancient history, Mars flowed with water over large portions of its surface – a wet world truly different than the Mars of today.
Did life perhaps thrive in the waters of ancient Mars? Conditions may have been too salty or acidic, at least for life as known on Earth, but perhaps not.
Mars echos, but moons in the Solar System – Europa, Titan, Enceladus – ring out, now, with the real possibility of harboring life.
Archaea are a type of microorganism – a relatively simple, ancient form of life, and yet intriguing.
Extant since early in the history of life on Earth, and still widely
Archaea, in high magnification, public domain image, available at http://en.wikipedia.org/wiki/Archaea
distributed on Earth today, archaea include extremophiles: microorganisms that thrive in extreme environmental conditions. For example, certain extremophiles live in highly saline water environments (halophiles), extremely hot water environments such as the hot spring depicted above (thermophiles) and extremely cold water environments (cryophiles or psychrophiles).
Extremophiles are particularly interesting to astrobiologists, who attempt to identify environments beyond earth that may harbor life – environments that are often extreme by Earth standards.
As an important example, microorganisms, including archaea, have been found to thrive around hydrothermal vents, which are essentially underwater volcanoes. These microbes use chemicals in the heated, mineral rich water for energy (leading to entire ecosystems there). Yet hydrothermal vents are evidently not unique to Earth, even in the Solar System; they are thought to likely exist, for example, on Europa, moon of Jupiter, as well as Titan and Enceladus, moons of Saturn. If archaea can thrive around earth’s hydrothermal vents, could microorganisms thrive around hydrothermal vents on Europa, Titan, Enceladus and elsewhere beyond Earth?
