• Mars vs. Europa: Are we looking in the wrong place for alien life?

    NASA / JPL-Caltech / MSSS

    This graphic shows the relative sizes of Earth, Mars and Europa, an icy moon of Jupiter.

    By Alan Boyle, Science Editor, NBC News


    A British astrobiology conference has revived a years-old debate over the best place to look for life elsewhere in the solar system: Mars, or the moons of Jupiter and Saturn?

    "For reasons I don't really understand, the wider solar system and the potential for life there has not been high priority," The Telegraph quoted Robert Pappalardo, a senior research scientist at NASA's Jet Propulsion Laboratory, as saying on BBC Radio 4.

    Pappalardo's remarks were occasioned by this week's astrobiology conference at the UK Center for Astrobiology in Edinburgh, Scotland. The center recently established the International Subsurface Astrobiology Laboratory, or ISAL, half a mile (1 kilometer) beneath the surface in Yorkshire's Boulby mine. Biologists will use that facility to see how organisms hold up in extreme environments, learn about life's chemical signatures, and test instruments that could look for those signatures on other worlds.

    Someday, one of the worlds may well be Europa, an icy moon of Jupiter. With a diameter of 1,945 miles (3,130 kilometers), Europa is just slightly smaller than Earth's moon, and yet it is thought to contain more water than Earth's oceans beneath a miles-deep layer of ice. Researchers recently suggested that hydrogen peroxide in the ice could serve as an energy supply for simple forms of life in the ocean hidden below.

    Europa is the focus of Pappalardo's research, and for months he has been urging NASA to support a $2 billion mission to study Europa at close range. However, proposals for NASA missions to Europa have been losing out, in part because of the cost of missions to Mars. Last week's federal budget proposal for the next fiscal year provides no funding for a Europa mission, but it does fund Mars missions such as Maven (launching this year), InSight (launching in 2016) and a new science rover (launching in 2020).

    Kevin Hand (JPL-Caltech) / Jack Cook (WHOI) / Howard Perlman (USGS)

    If Europa's ocean is 100 kilometers (62 miles) deep, and all that water were gathered into a ball, it would have a radius of 877 kilometers (545 miles). This graphic compares that hypothetical ball of Europan water to the size of the Jovian moon itself, as well as all the water on planet Earth. Europa is thought to have two to three times the volume of water in Earth's oceans.

    At February's annual meeting of the American Association for the Advancement of Science, Pappalardo worried that NASA's study of the outer solar system would go "radio-dark" in 2017, when the Cassini mission to Saturn and the Juno mission to Jupiter are both due to end. He continued that theme in this week's BBC interview.

    "I worry that if Europa exploration is delayed, but then finally it happens some day, we might look back and say 'Why didn't we do that sooner?' Imagine 50 years from now, we get a lander there and find signs of life. All this time we'll have been looking in the wrong place," he was quoted as saying.

    Europa isn't the only moon that intrigues astrobiologists: In the Jovian system, Callisto and Ganymede also have icy shells and may hold hidden oceans. Meanwhile, Cassini has repeatedly observed geysers of water ice rising from the surface of the Saturnian moon Enceladus — suggesting that liquid water and perhaps life may lie beneath the surface. Saturn's largest moon, Titan, has a thick atmosphere and seas of hydrocarbon that some scientists think could harbor a totally alien kind of life.

    As for Mars, astrobiologists say hints of life could well lurk beneath the surface. To some extent, the Red Planet has been winning out over Europa and Enceladus because it's easier to get to. Moreover, NASA's vision calls for sending astronauts to Mars and its moons in the 2030s. NASA's robotic missions serve as precursors for those human voyages, as well as steps in a long-term program to learn about life in the universe.

    Europa's fans can take heart in the fact that the European Space Agency is planning its own mission to Jupiter's moons: The Jupiter Icy Moons Explorer, or JUICE, is due for launch in 2022 and arrival at the Jovian system in 2030. There's also talk of a sample return mission that would target Enceladus' geysers, and a proposal to drop a boat onto Titan's seas.

    So what if all of these worlds — Mars and Europa, Callisto and Ganymede, Titan and Enceladus — turn out to be lifeless? Charles Cockell, who heads the UK Center for Astrobiology, addressed that scenario in an interview with the BBC.

    "A lot of people think astrobiology is some sort of hunt for life, and if we don't find life, it will be a big disappointment," Cockell said. "But in fact, that's not the case. The discovery of many lifeless planets across the universe, the discovery that the Earth might be unique as a place for life, would be an astonishing discovery in itself. It would be a very lonely discovery, but it would be an astonishing discovery."

    More about the search for life:

    Alan Boyle is NBCNews.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter and adding the Cosmic Log page to your Google+ presence. To keep up with Cosmic Log as well as NBCNews.com's other stories about science and space, sign up for the Tech & Science newsletter, delivered to your email in-box every weekday. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for new worlds.

  • Outlook dims for interplanetary trips

    NASA

    An artist's conception shows the Jupiter Europa Orbiter with the Jovian moon Europa in the foreground.

    By Alan Boyle, Science Editor, NBC News

    Last updated
    11:35 a.m. ET March 8:

    Planetary scientists would love to have some samples collected on Mars for delivery back to Earth, and they're itching to get a closer look at Europa, a moon of Jupiter that may harbor a hidden ocean and perhaps life as well. But they might be stymied during the decade to come, due to the federal government's tightening financial circumstances.

    The Mars and Europa missions are the top priorities for flagship robotic missions emerging from a big-picture scientific assessment known as the Decadal Survey. Over the past couple of years, the survey's organizers have received input from more than 1,600 planetary scientists, and the final results were released today in the form of a National Research Council report titled "Visions and Voyages."

    The whole idea of the survey is to let scientists weigh in on NASA's priorities for exploration over the coming decade. Two big-ticket missions — the Mars Astrobiology Explorer-Catcher, or MAX-C, and the Jupiter Europa Orbiter — rose to the top:

    • MAX-C, proposed for launch in 2018, would gather up rocks and soil from a promising area of the Red Planet and have the stuff ready to blast into Martian orbit, where it could be picked up for eventual return to Earth. Such a mission would lead to the first opportunity to examine fresh material from Mars, which could hold clues to the existence of past or present life on Mars.
    • The Jupiter Europa Orbiter is proposed for launch in 2020 and would reach the Jovian system in 2025 or so. The spacecraft would focus on Europa and two other moons of Jupiter that may have subsurface oceans of water, Callisto and Ganymede. Ice-penetrating radar could determine how close liquid water is to the surface of those moons, and detailed chemical analysis of Europa's top layer could conceivably turn up signs of life.

    The only problem is, doing these sorts of things costs money. A lot of money. The report notes that the mission to Jupiter and Europa is projected to cost $4.7 billion, and MAX-C's projected cost is $3.5 billion. It suggests that MAX-C would have to be cut back to $2.5 billion, and that the Jupiter Europa Orbiter mission should proceed in the 2013-2022 time frame "only if changes to both the mission and the NASA planetary budget make it affordable without eliminating any other recommended missions."

    The exploration situation could get even tougher due to the budget-cutting mood in Washington. If there's less money than projected for planetary exploration, NASA should consider not only cutting back on the scope of those flagship missions, but delaying or canceling them, the report says.

    ESA

    This illustration shows one of the concepts for Europe's ExoMars rover at left, and NASA's MAX-C collection rover at right.

    The future of NASA's robotic exploration is further complicated by the fact that both MAX-C and the Jupiter Europa Orbiter are being considered in cooperation with the European Space Agency. MAX-C would be complemented by ESA's ExoMars rover, and the Europeans have been willing to sign up as partners in the Europa study effort. Shifts in cost and scope could affect the character of international cooperation in robotic space exploration.

    What's more, NASA has other types of programs to think about: The International Space Station is likely to be in operation well into the 2013-2022 period, and Congress wants the space agency to spend billions on the development of a next-generation heavy-lift rocket for human spaceflight. Meanwhile, the Decadal Survey's report on astrophysics — released last August — has rolled out a separate wish list with pricey items, including a $1.6 billion space telescope to probe dark energy and identify Earthlike planets.

    Game plan for future missions
    The survey's chairman, Cornell University astronomer Steve Squyres, discussed the 400-page report in depth today during the Lunar and Planetary Science Conference in Texas. He laid out a game plan for matching the aspirations of planetary scientists with the available budgets:

    • See if MAX-C and ExoMars can be combined into a one-rover sample collection mission to Mars. He said an analysis of the mission requirements suggested that such a mission could be done for $2.5 billion, even if NASA had to do it alone.
    • If MAX-C's cost to NASA can't be brought down to $2.5 billion, the mission should be taken off the table. "There's no Plan B," said Squyres, who heads the science team for the wildly successful Mars rover missions. The Jupiter Europa Orbiter would become the prime focus for flagship missions, but the cost would have to be reduced. "It is a fabulous mission, but at 4.7 [billion dollars] it is an intractable problem that needs to get fixed," Squyres said.
    • If neither of those two missions can be done in the 2013-2022 period, consider sending an orbiter and atmospheric probe to Uranus. Cost of that mission, which would be the first to focus exclusively on an ice giant planet, is estimated at $2.7 billion, "so it ain't cheap either," Squyres said.
    • The next priorities would be the Venus Climate Mission (at $2.4 billion) or the Enceladus Orbiter (at $1.9 billion). "If you can't afford any of those, you've got no flagships at all," Squyres said.

    Under that scenario, big-ticket missions would go by the wayside for the next decade, leaving NASA with medium-class missions such as Juno, a solar-powered Jupiter orbiter with a cost of $1 billion; and lower-cost efforts such as the GRAIL lunar probes, which carry a price tag of $375 million. Squyres said those types of programs should not be cut back. The scientists also endorsed the Mars Trace Gas Orbiter, a NASA-European mission that would be launched in 2016 to delve into the mystery of Martian methane.

    Wide array of future flights
    The report suggests seven candidates for future medium-class missions, which would be selected through NASA's New Frontiers program. Such missions could bring a sample back from the surface of a comet, explore the lunar south pole, analyze Saturn's atmosphere, explore the Trojan asteroids that share Jupiter's orbit, land on the surface of Venus, observe the Jovian moon Io, or distribute sensors around the moon to study lunar seismology.

    On another front, the decadal report recommends setting aside 6 to 8 percent of NASA's planetary science funding for technology development and urges the federal government to restart production of plutonium-238. That radioisotope is used to power missions heading for the outer solar system, where solar power just isn't enough to keep a spacecraft warm and working.

    Squyres urged the researchers assembled in Texas to contact their representatives in Congress and voice their support for the exploration plan.

    Jim Green, the director of NASA's Planetary Science Division, said that tough economic times may lie ahead, and the scientific community's backing would be critical in the years to come. "The decadal report transcends Congress, transcends changes in administration, and is our guiding light that moves us forward, year after year after year," he said.

    Correction for 11:35 a.m. ET: An earlier version of this report incorrectly suggested that Green called on scientists to contact members of Congress. That call actually came from Squyres.

    Join the Cosmic Log community by clicking the "like" button on our Facebook page or by following msnbc.com science editor Alan Boyle as b0yle on Twitter. To learn more about Alan Boyle's book on Pluto and the search for planets, check out the website for "The Case for Pluto." 

  • Scientists to probe for life on Jupiter's moons?

    ESA / NASA / Michael Carrol

    The joint NASA-ESA Europa Jupiter System Mission would send to orbiters to explore the Jovian moons Europa and Ganymede. It is one of three missions vying to be the next big mission put on by the European Space Agency.

    By John Roach, Contributing Writer, NBC News

    Scientists may finally get a chance to probe Jupiter's moons Europa and Ganymede for signs of microbial life, by looking in what are thought to be liquid oceans beneath their frozen crusts.

    The Europa Jupiter Systems Mission is one of three finalists vying to carry out the European Space Agency's next big mission. All three presented mission plans Feb. 3 at a conference in Paris. A final decision is expected this June.

    The other two missions vying for funding are the International X-ray Observatory, which could reveal what happens in the vicinity of black holes, and Laser Interferometer Space Antenna, which will "listen" to gravitational waves, giving space-time a sort of soundtrack.

    Jupiter moons
    All three missions are international collaborations, so Europe's decision is tied to and will have consequences for the priorities of NASA, a partner on all three, and the Japan Aerospace Exploration Agency, a partner on IXO.

    Under the joint NASA-ESA Europa Jupiter Systems Mission, NASA will target Europa, an ice-covered moon thought to harbor a liquid ocean beneath its crust; ESA will head to Ganymede, the largest moon in the solar system.

    Since the two orbiters are built by different agencies, one could fly without the other, though "you get better results in tandem," noted Michele Dougherty of University College London, who made the case for the joint mission at the Paris meeting, according to Space News.

    Having two spacecraft, for example, would give scientists an opportunity to study Jupiter's atmosphere and magnetosphere in three dimensions.

    International collaboration
    IXO and LISA are considered too big and complicated to fly without international collaboration. Currently, IXO's lack of technical readiness has prompted the U.S. National Academy of Sciences to rank it a lower than LISA for U.S. space-science priorities.

    Boosters of both missions say technical hurdles can be cleared and will be well worth the effort. IXO promises to provide the sharpest and most sensitive X-ray views of the Universe, according to team member Kirpal Nandra.

    Bernard Schutz, a director at the Albert Einstein Institute in Golm, Germany, likened LISA's ability to "hear" gravitational waves, which are ripples of space-time, would be like adding sound to a silent film of a walk through a jungle. "There are bound to be many things we didn't even expect," he told Nature News.

    Which mission is set as a priority in Europe will become clearer this June. NASA has thrown preliminary support behind all three, though guidelines to be laid out March 7 in the final version of the National Academy of Sciences ranking will set the space agency's agenda.

    Keep in mind, all the missions are still way out on the horizon: The one ultimately selected wouldn't launch until around 2020.

    For more about these missions, check out these stories:

    John Roach is a contributing writer for msnbc.com. Connect with the Cosmic Log community by hitting the "like" button on the Cosmic Log Facebook page or following msnbc.com's science editor, Alan Boyle, on Twitter (@b0yle).