Space & Innovation

NASA's Europa Mission May Land on Ocean-Harboring Moon

NASA is exploring the idea of putting a lander on Europa to look for signs of life.

NASA's upcoming mission to Europa may actually touch down on the potentially life-harboring Jupiter moon.

While the main thrust of the Europa mission, which NASA aims to launch by the mid-2020s, involves characterizing the icy satellite from afar during dozens of flybys, the space agency is considering sending a small probe down to the surface as well.

"We are actively pursuing the possibility of a lander," Robert Pappalardo, Europa project scientist at NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, said last week during a panel discussion at the American Institute of Aeronautics and Astronautics' Space 2015 conference in Pasadena. (JPL manages the Europa mission.) [Europa May Harbor Simple Life-Forms (Video)]

Photos: Exquisite Exoplanetary Art

"NASA has asked us to investigate: What would it take? How much would it cost? Could we put a small surface package on Europa with this mission?" Pappalardo added.

NASA has also asked the European Space Agency if it would be interested in contributing a lander, ice-penetrating impactor or other piggyback probe to the roughly $2 billion Europa mission, Spaceflight Now reported in April.

Solar system's best bet for alien life?

The 1,900-mile-wide (3,100 kilometers) Europa is covered by an ice shell perhaps 50 miles (80 km) thick, but underneath this crust is thought to lie a huge ocean of liquid water 12 miles (20 km) deep or so.

At least five other moons in the solar system - the Jovian satellites Ganymede and Callisto, Saturn's Enceladus and Titan and the Neptune moon Triton - are believed to harbor such subsurface seas, Kevin Hand, deputy chief scientist at JPL's Solar System Exploration Directorate, said during the same panel discussion at Space 2015.

But only the oceans of Enceladus and Europa are likely in contact with the rocky mantle, a scenario that makes all sorts of interesting chemical reactions possible, he added. (The other moons' oceans are probably sandwiched between layers of ice.)

NASA's Europa Mission Will Look for Life's Ingredients

So Europa and Enceladus are the top two destinations on many astrobiologists' mission wish lists. Hand gives the Jovian moon a slight edge, though.

Researchers know enough about Europa to surmise that its ocean has existed since the dawn of the solar system 4.5 billion years ago, giving putative lifeforms plenty of time to evolve, Hand explained. Modeling work about the 310-mile-wide (500 km) Enceladus is less mature, so it's unclear how long the Saturn satellite has harbored its sea.

"When it comes to habitability, we'd like to have the knowledge that the potentially habitable environment has been there for a significant duration," Hand said.

But enthusiasm about a possible Enceladus mission is high as well, especially because the Saturn moon's powerful geysers offer a way to sample its ocean from afar. Indeed, NASA is considering a potential mission called Enceladus Life Finder (ELF) that would do just that.

The Europa flyby mission

While ELF remains a concept at this point - it's competing with about two dozen other proposals to become the next mission in NASA's low-cost Discovery Program - the Europa project is officially on the space agency's books.

The as-yet-unnamed Europa mission could launch as early as 2022. After reaching Jupiter orbit, the robotic probe will perform 45 flybys of Europa over the course of 2.5 years or so.

During these flybys, the spacecraft will scrutinize Europa using nine different science instruments, including high-resolution cameras, a heat detector and ice-penetrating radar. The mission's observations should teach scientists a great deal about the moon's surface composition, the nature of its underground ocean and its ability to support life as we know it, NASA officials have said. (Actively hunting for signs of life is not part of the current plan.)

Photos: The Moons of Jupiter

The flyby mission should also serve a reconnaissance function. NASA has expressed interest in sending a dedicated lander mission to the icy moon - perhaps one that even attempts to get under Europa's ice shell - but doesn't feel ready to do so yet.

"We actually don't know what the surface of Europa looks like at the scale of this table, at the scale of a lander - if it's smooth, if it's incredibly rough, if it's full of spikes,"Curt Niebur, Europa program scientist at NASA's Washington headquarters, said during a June news conference that announced the mission's science payload. "Without knowing what the surface even looks like, it's difficult to design a lander that could survive."

But that lack of knowledge is less of a concern when the lander under consideration is a low-cost add-on to an existing mission, rather than a billion-dollar, stand-alone project.

That appears to be NASA's reasoning, anyway. And we should soon know more about the prospects of a lander blasting off with the Europa flyby probe relatively soon.

"By the end of this year, we should have an idea of how that's looking," Pappalardo said at the Space 2015 conference.

Originally published on Space.com.

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Europa is a prime candidate for alien life.

On August 4, the much-anticipated "Wonders of the Solar System" documentary will premier on the Science Channel.

Presenter and physicist Prof. Brian Cox will show you the hidden mysteries of our interplanetary neighborhood, as well as breathtaking sights of the planets, moons and the sun. Cox will also examine some of Earth's extreme environments to see how life has adapted, perhaps helping us understand whether life can exist elsewhere in our solar system. To provide a taster of what you can expect from "Wonders," Discovery News has gathered some facts, figures and the best images of our solar system to assemble a special Wide Angle supporting this groundbreaking documentary. Let's begin, in the orbit of the solar system's biggest planet, Jupiter...

Moons of Jupiter: Io

Welcome to Jupiter, the solar system's biggest planet and host to more than 63 peculiar moons -- a steady contender for moons compared to satellite-strewn Saturn. From sulfur-spewing furnaces to ice-encrusted oceans, these Jovian satellites are anything but normal! Browse through 10 of our favorites here. If you're looking for a fiery, volcanic spectacle, head to Io, the innermost of Jupiter's "big four" moons. Jupiter's gravity pulls at Io so strongly that the land has tides of up to 300 feet (100 meters). This gravitational tug-of-war produces scorching heat and raises more volcanic activity here than anywhere else in the solar system. Io has a sulfurous surface, and its volcanoes spew silicate magma, causing the hellish moon's surface look like a pizza.

Moons of Jupiter: Metis

While it doesn't look like much in this image (the highest-resolution available!), Metis is Jupiter's closest companion -- for now. It's orbiting the gas giant at a distance of just 75,500 miles (128,000 kilometers) and moving faster than Jupiter spins. Metis is so close to Jupiter's surface, in fact, that it will gradually succumb to the planet's gravity and plunge into its churning clouds. This same principle applies to man-made satellites orbiting the Earth; if their orbit is too low, they'll eventually fall.

Moons of Jupiter: Adrastea

Like Metis, Adrastea is on its way down, eventually: Its orbit is just 1,000 kilometers (621 miles) outside of its fellow doomed moon. The two bodies probably provide lots of the material making up Jupiter's main ring, shown in this Galileo spacecraft image. Adrastea is also tiny at a wee 12 miles (20 kilometers) in diameter.

Moons of Jupiter: Ganymede

If Ganymede orbited the sun instead of Jupiter, it would be a planet of its own -- it's even bigger than Mercury. Its interior is made from layers surrounding a rocky core, and its surface is covered in water ice. Although Ganymede doesn't have much of an atmosphere, it does have some ozone gas near its surface. This gas comes from charged particles in Jupiter's magnetic field smacking into the moon's icy crust.

Moons of Jupiter: Themisto

We're not entirely sure what Themisto looks like, but scientists know it one odd little satellite. Unlike most other moons, Themisto is oblong and doesn't fit into the traditional groups of Jovian moons. Because this body is so small -- just 5 miles (8 kilometers) in diameter -- astronomers in 2000 confused it for a new object when it was originally found in 1975. Shown here is a speculative illustration of how the irregular moon might be shaped.

Moons of Jupiter: Callisto

Along with Io, Ganymede, and Europa (which is yet to come in this slide show), Callisto is one of the four Galilean satellites. These are the moons of Jupiter that Galileo discovered while looking through a telescope in 1610. Callisto is about the same size as Mercury, and it's a heavily cratered moon that has almost no geological activity. Callisto's surface may also be one of the oldest landscapes in the solar system, including Earth's moon -- about 4 billion years old.

Moons of Jupiter: Thebe

Along with Metis and Adrastea, Thebe was discovered by scientists studying images from the Voyager spacecraft in 1979 and 1980. It's closer to Jupiter than Io is, but it's not so close that it's in danger of losing its altitude. The material in Jupiter's Gossamer ring probably comes from Thebe and another moon, Amalthea.

Moons of Jupiter: Amalthea

Speaking of Amalthea, shown here is an artist's rendition of the mysterious moon (inset: our best real view so far). Astronomers don't know much about it, but they do know it's the reddest body in the solar system. Unlike the other three moons that lie within Io's orbit -- Thebe, Metis and Adrastea -- Amalthea wasn't discovered by the Voyager science team. Edward Emerson Barnard discovered Amalthea it in 1892, and it had been almost 300 years since anyone had discovered a new moon orbiting Jupiter. Before that, the last person to discover a Jovian moon was Galileo.

Moons of Jupiter: S/2000 J11

This not-to-be-named moon marks an interesting dividing line in the wealth of satellites orbiting Jupiter. S/2000 J11, named after it was found in 2000, moves in the same direction that Jupiter spins -- as do all the moons that are closer to the planet. Almost every distant moon, however, orbits in the opposite (retrograde) direction, as this diagram shows. The only known exception is Carpo, sometimes known as Karpo, which was discovered in 2003.

Moons of Jupiter: Europa

About two-thirds of the Earth is covered in water, but Europa has about twice as much water as our home planet. Europa's might surface is covered in ice, but astronomers are almost convinced there is an ocean of liquid water underneath -- an environment shielded from Jupiter's intense radiation that might be hospitable to life. A cold, salty planet might not seem like a good place to live, but there are species on Earth that thrive in just those conditions.

Slideshow originally posted Feb. 2009.