Dec 16, 2013 04:10 PM ET
Could Europa Discovery Spur Life-Hunting Mission?
In light of last week's announcement of Hubble's detection of huge plumes of water vapor over Europa's south pole, this could be the motivation the world needs to send a life-hunting mission to Jupiter's mysterious icy moon.
NASA, ESA, and M. Kornmesser.
Based on observations by the hubble Space Telescope, this artist's impresion shows the water-laced plumes hanging over Europa, with Jupiter as the backdrop.
Cowboys & Aliens are Coming!
July 29, 2011 -- If aliens are going out of their way to kick up dust in the Wild West, as they do in the upcoming movie "Cowboys & Aliens," they must be coming from somewhere.
Life could take root on a moon or a meteorite. But to nurture the kind of life that could destroy our saloons and harass our livestock, a planet might be the most suitable.
So far, Kepler, a NASA orbiting telescope that searches for planets beyond our solar system, has detected over 1,200 exoplanets. Surely there must be a few candidates among this group that could meet some of the most basic requirements to host life?
Explore some far-out worlds that could support aliens, be they cattle-rustling characters or a more peaceful people.
First, let's lay out some basic criteria. Kepler hasn't identified many rocky worlds and a solid surface is essential for life to take root.
Size matters: The mass of the planet helps astrophysicists infer what it's made of. Some planets are Earth-sized. Others are several times the size of our planet. And then there are gas giants, which can range from "Neptune sized" to "super-Jupiters."
Orbit: To support life, a planet must be in a stable orbit around its star -- no planets with wonky orbits that will eventually dump them into their star for a fiery death. Goldilocks Zone: This is a region not too hot or too cold that gives the planet enough distance from its parent star to have liquid water, key for life.
Loner Stars: Single stars make better parents. In 2010, a pair of closely orbiting binary stars was spotted surrounded by what could be the debris of former planets.
Unknowns: Some factors for life can't be confirmed one way or the other from the data available about extrasolar planets. These include: water, chemical compounds such as ammonia; a nitrogen-rich atmosphere; a magnetic field to repel solar and cosmic radiation; and more.
BUT, some planets do have a head-start, beginning with Gliese 581D.
ESO/L. Calçada
Gliese 581d
Located a mere 20 light-years away, practically our backyard in cosmic terms, Gliese 581d is situated on the "outer fringes" of the Goldilocks zone, orbiting a red dwarf star.
The planet may be warm enough and wet enough to support life in much the same manner as Earth. It might also contain a thick carbon atmosphere.
If we ever need a new Earth and have the means to get there, Gliese 581d may be our best bet for now.
When it was first detected and reported last year in Astrophysical Journal, Gliese 581g appeared to be the perfect candidate for a true "Earth-like" planet. Located in the same star system as Gliese 581d (and detected earlier), Gliese 581g seemed to be the right size and located within a habitable zone away from its parent star. Gliese 581g was said to have three times the mass of Earth, making it possible for the planet to hold an atmosphere.
However, since its discovery, follow-up studies have alleged that Gliese 581g might have been a false alarm. In other words, the planet might not exist at all.
Dubbed a "waterworld" and located a mere 42 light-years from Earth, GJ 1214b orbits near a red dwarf star about one-fifth the size of our sun.
What makes this planet unique is that it appears to be primarily composed of water, although GJ 1214b is 6.5 times the mass of Earth and 2.7 times wider, which classifies it as a "super-Earth."
This planet also has a steamy atmosphere composed of thick, dense clouds of hydrogen, which, although it might not the case with this planet, could incubate life.
Situated 150 light-years from Earth, HD 209458b is a planet that holds traces of water vapor in its atmosphere, and also contains basic organic compounds that, on Earth, foster the development of life.
But there are two factors working against HD 209458b as a suitable habitat. The planet is very hot due to its close proximity to its parents star, and it's a gas giant, so no solid surfaces.
If Kepler-10b were located further from its parent star, it might have had a chance of hosting life. Kepler-10b was the first "iron-clad proof of a rocky planet beyond our solar system" back in 2001. It was even dubbed the "missing link" of extrasolar planetary research.
When it comes to the search for life, though, Kepler 10-b is missing a lot of other ingredients -- just minor things like water or an atmosphere.
When venturing to a new star system to explore the possibility of extraterrestrial life, trying a star that has already shown itself to nurture planets -- even if they're not the kind you're looking for -- could be a promising strategy.
Project Icarus, an ambitious five-year study into launching an unmanned spacecraft to an interstellar destination, has identified two stars located within 15 light-years that might fit the bill: "epsilon Eridani, a single K star 10.5 light-years away, and the red dwarf GJ 674, 14.8 light-years away."
Indirect evidence has also shown that epsilon Eridani may already hold smaller worlds scientists simply haven't detected yet.
Also, red dwarf star systems generally may be a safe haven for life.
Taking into account the number of exoplanets that have been detected, as well as the vastly greater number that are estimated to be out there, some astrophysicists are convinced that extraterrestrial life is inevitable. After all, the Milky Way may be loaded with as many as 50 billion alien worlds. Some even think we'll find alien life by 2020.
Others, however, say it may not exist at all.
Recently, astrophysicists David Spiegel of Princeton University and Edwin Turner from the University of Tokyo suggested we might be alone in the universe, based on their interpretation of the Drake equation, a formula meant to determine loosely the probability of the existence of life beyond Earth. According to their analysis, just because life on Earth took shape early, endured and prospered doesn't mean the same process would naturally and inevitably occur elsewhere in the universe.
Discovering life elsewhere, however, would be the only means of settling this debate.
Unless the aliens find us first, of course.
As we celebrate China's successful Chang'e 3 landing on the moon, the world's media is abuzz with images of rocky, dusty alien landscapes once more. Granted, the images are notable in that we haven't seen new photographs from the lunar surface since the last soft moon landing some 36 years ago, but, like the images from NASA's Mars missions, it's all parched rock and dust for as far as the eye can see.Wouldn't it make a change to see visas filled with huge blocks of broken ice potentially laced with organic chemistry? In light of last week's announcement of Hubble's detection of huge plumes of water vapor over Europa's south pole, this could be the motivation the world needs to send a life-hunting mission to Jupiter's mysterious icy moon.NEWS: Hubble Discovers Water Plumes Over EuropaEuropa contains a vast liquid water ocean beneath its icy crust. The moon is heated from within  -  tidal interactions with its parent gas giant generates the energy needed to maintain the liquid ocean  -  while the icy crust shields the ocean against the high-radiation space environment. The moon also has an active surface layer where the ocean interacts with the surface, producing tell-tail compounds such as magnesium sulfate. Calculations have also shown that there is likely enough oxygen cycling in the water to support a huge hypothetical biomass.And now, Europa appears to be generating plumes of water vapor, jetting into space from geysers blasting through fissures. Could these plumes be holding the secret to Europa's biological potential?"Indeed, the plumes are incredibly exciting, if they are there," said Jim Green, head of NASA's planetary science division, at the American Geophysical Union (AGU) last week in San Francisco. "They're bringing up material from within the ocean; perhaps there's organic material that will be laying on the surface of the south pole."ANALYSIS: Is Europa Too Prickly to Land On?Interest has always been high in the life-giving potential of Europa and many mission ideas have been formulated, namely the Europa Clipper concept.Consisting of a Jupiter orbiter, the Clipper would make several flybys of the icy moon, observing the 1,900 mile-wide world on each pass. The Clipper was identified last year as the most "cost effective" way of studying Europa last year and the concept appears to be gaining traction.The detection of water vapor plumes only make this mission even more tantalizing  -  the Europa Clipper could be outfitted with instrumentation that could analyze the chemistry of the tenuous gas, much like NASA's Cassini mission has done by flying through the water vapor plumes over the Saturnian moon Enceladus."Based on these (new) observations, we're going to redouble our efforts to take a good look at Clipper  -  its orbital trajectories, the plans for the mission architecture  -  to ensure that we have the right instrumentation and that we can cover this area very well and really, really understand it," said Green.NEWS: Convection May Explain Europa's Weird Chaotic TerrainUnfortunately, as NASA's already minuscule budget gets tightened even more, threatening the entire planetary sciences division, such a mission seems unfeasible for the foreseeable future. As pointed out by Green, the Europa Clipper would cost around $2 billion, making the concept a "flagship mission." So unless some big changes are made to NASA's fiscal woes, the Clipper will likely be on ice for several years to come.That's not to say other space agencies aren't eying the enigmatic moon. The European Space Agency is currently planning the Jupiter Icy Moon Explorer, or JUICE, mission for a 2022 launch. The spacecraft will carry out flybys of Ganymede, Callisto and Europa, but as noted by SPACE.com's Mike Wall, JUICE will only fly past Europa twice.Flybys are all well and good, but until we physically land a robotic mission onto Europa's surface, returning photographs of stunning landscapes of dirty ice, we'll never fully appreciate the life-giving potential Europa appears to possess.More Discovery News coverage of missions to Europa:A Jovian Mystery: It's Time to Land On EuropaWill the Europa Clipper Cruise to Jupiter's Moon?Will NASA Boldly Go to Europa?Source: SPACE.comImage: Based on observations by the hubble Space Telescope, this artist's impresion shows the water-laced plumes hanging over Europa, with Jupiter as the backdrop. Credit: NASA, ESA, and M. Kornmesser