NASA has unveiled the beautiful faces of far-off worlds like Mars, Jupiter, and Pluto, but there's one face it has yet to see: the surface of Jupiter's moon Europa, which is one of the most likely candidate worlds for alien life in our solar system.
Now, after years of studies to determine which spacecraft is best for the job, NASA is taking steps toward a $2 billion Europa mission — called the Europa Multi-Flyby Mission — that could launch some time in the 2020s and finally settle the debate over whether alien Europans exist or not.
Mission scientists are still finalizing the design, but at its simplest, the mission will involve a spacecraft that performs dozens of flybys above Europa's surface.
"Anything else we can add to the flyby mission, whether it's a lander or any kind of probe, will make it even more fantastic but even without those things this is going to be a mission that's one of the best that NASA's ever done in terms of the science return and the excitement it generates," Curt Niebur, who is the lead program scientists for NASA's New Frontiers Program, told Business Insider.
More than anything else, NASA wants to determine whether Europa is habitable or not. Scientists know that it contains a giant ocean beneath its surface that could contain more water than all of Earth's oceans combined. But does that water harbor the conditions for life?
"What if the ocean has a pH of 1 (too acidic), or what if it doesn't have the basic building blocks that life needs?" Niebur said. "What Europa [flyby mission] is going to do is answer that question and tell us what are the conditions inside the ocean."
Check out all the coolest celestial events you can catch this year:
2016 space calendar
'This is going to be a mission that's one of the best that NASA has ever done'
January 3, 4 - Quadrantids Meteor Shower
You may still have some leftovers from that New Years Eve when the first meteor shower of the year hits its peak. On Sunday evening you'll have a chance to catch up to 40 meteors per hour at peak, but the shower runs annually from January 1-5. Keep your eye on the constellation Bootes for the best chance of seeing one.
(Photo via NASA/MSFC/MEO)
March (date uncertain)
This one will likely be easier to watch on your smartphone via livestream, but sometime in March Astronaut Scott Kelly and Cosmonaut Mikhail Kornienko are scheduled to return to Earth after their groundbreaking "Year in Space" mission on board the International Space Station -- they've already been having a blast.
(Photo via AOL)
March 9 - Total Solar Eclipse
Skywatchers will be treated to a total solar eclipse in early March. The best views will be seen in central Indonesia and the Pacific Ocean where the sun will be fully blocked. A partial eclipse will be visible in most parts of northern Australia and southeast Asia. If you can't be in that part of the world, keep your eye out for the livestream.
(Photo via GREG WOOD/AFP/Getty Images)
March 20 - Spring Equinox
The vernal or spring equinox (for the Northern Hemisphere, at least) occurs when the Sun shines directly on the equator and there is nearly equal amounts of day and night throughout the world. It also signals first day of spring for those north of the equator and the first day of fall (autumnal equinox) in the Southern Hemisphere. For those with the freedom to travel who are looking for a great view, Stonehenge is one of the best places in the world to mark this day.
(AP Photo/Dan Joling)
March 23 - Penumbral Lunar Eclipse
The Moon will darken slightly but not completely during this eclipse which occurs when the Moon passes through the Earth's partial shadow, or penumbra. The eclipse will be visible throughout most of extreme eastern Asia, eastern Australia, the Pacific Ocean, and the west coast of North America including Alaska.
(AP Photo/Bullit Marquez)
April 22 - Full Pink Moon
One of many full moons in 2016, the April moon was known by Native American tribes as the Full Pink Moon because it typically shows up when the pink flowers of spring return. This year's will be noteworthy because it coincides with a meteor shower.
(Photo by Franco Origlia/Getty Images)
April 22, 23 - Lyrids Meteor Shower
The Lyrids shower runs from April 16-25. This year it will peak on the same night as as the full moon, which will make all but the brightest meteors hard to see. For the best chance, keep your eye on the constellation Lyra.
(Photo by Fatma Selma Kocabas Aydin/Anadolu Agency/Getty Images)
May 6, 7 - Eta Aquarids Meteor Shower
You might not know this shower well, but you probably know the celestial body that causes it: Halley's Comet. For those in the Southern Hemisphere, this is a big shower, with up to 60 meteors per hour at its peak. Up north, expect more like 30 meteors per hour. The shower runs from April 19 to May 28 and peaks on the evening of May 6 and coincides with a new moon (no moon) which means darker skies and likely a better show. Look to the constellation Aquarius for this one.
(Photo via NASA)
May 9 - Rare Transit of Mercury Across the Sun
You'll want to find a telescope and good solar filter to check out this view, as Mercury will passes between the Earth and the Sun. This is extremely rare event occurs only once every few years, and other than one other transit in 2019, we won't have a chance to see Mercury pass over the Sun until 2039. While this one will be visible throughout North America, Mexico, Central America, South America, and parts of Europe, Asia, and Africa, those on the East Coast of the U.S. and east side of South America will get the best views.
(Photo by SSPL/Getty Images)
May 21 - Blue Moon
The the third of four full moons in this season, the May 21 full moon is known as a blue moon. This rare calendar event only happens once every few years, giving rise to the term, “once in a blue moon.” There are normally only three full moons in each season of the year, but fourth "blue" moons pop up every 2.7 years on average. Unfortunately, they are not actually blue.
(Photo credit should read ROBERT ATANASOVSKI/AFP/Getty Images)
May 22 - Mars at Opposition
If you want to snap a picture of Mars, this is your best chance in 2016 (unless you happen to be a robot on Mars). The red planet will be at its closest point to Earth and its face will be fully illuminated by the Sun. A great time to photograph the planet, it's also a great time to capture some of the details on the surface with a medium-sized telescope.
(Photo by: Universal History Archive/UIG via Getty Images)
June 3 - Saturn at Opposition
Mere days after Mars comes in for its close up, Saturn swings on by too. The ringed planet will be brighter than any other time of the year on the 3rd -- and you'll be able to see not only its famed rings, but also a handful of bright moons as well if you pick up a telescope.
(Photo by: Universal History Archive/UIG via Getty Images)
June 20 - June Solstice
The longest day and official start of summer in the Northern Hemipshere brings the shortest day in the Southern Hemisphere. It's another great chance to visit Stonehenge (you definitely won't be alone) or if you're the type of person who never wants the day to end, head up to somewhere like Anchorage, Alaska, where the day will last a full 22 hours.
(Photo credit should read DESIREE MARTIN/AFP/Getty Images)
July 4 - Juno at Jupiter
Hello Jupiter! NASA's Juno spacecraft is on pace to arrive at Jupiter after a five year journey on July 4, 2016. Launched on August 5, 2011, Juno will be inserted into a polar orbit around the giant planet to begin studying Jupiter’s atmosphere and magnetic field until October 2017, when it will go out in a blaze of glory as it crashes onto the planet's surface.
(Photo by Bill Ingalls/NASA via Getty Images)
July 28, 29 - Delta Aquarids Meteor Shower
Another great meteor shower that focuses on the constellation Aquarius, this one runs annually from July 12 to August 23 and peaks the night of July 28. The visible moon will block fainter meteors more than a few good ones should shine through.
The Perseids is consistently one of the best meteor showers for those who like to count "shooting stars" with up to 60 meteors per hour at its peak. This year's conditions are especially good for anyone willing to stay up late, since the waxing moon should set shortly after midnight. The meteors are produced by comet Swift-Tuttle, lasting from July 17 to August 24 and peaking on the night of August 12. Look to the constellation of Perseus for the best sight.
(Photo credit should read SERGEY BALAY/AFP/Getty Images)
August 27 - Conjunction of Venus and Jupiter
Though they are more than 400 million miles from each other typically, Venus and Jupiter will look like they're about to high five each other in August during a special conjunction. The two bright planets will appear to be only 0.06 degrees apart, if you keep your eyes to the west after sunset.
(AP Photo/Ted S. Warren)
September 1 - Annular Solar Eclipse
Annular solar eclipses occur when the Moon is further from the Earth and doesn't cast quite a big enough shadow to completely block the Sun's light, creating a ring of light in the sky. This annular eclipse will sweep from the eastern coast of central Africa and sweep across through to the Indian Ocean.
September 3 - Neptune at Opposition
If you have access to a telescope and want to catch a view of the blue giant planet, this is your best shot. Neptune will come closest to the Earth than any other time of the year, but at a distance of about 2.8 billion (on average) miles, you'll still need to find a powerful telescope to see it.
(Photo via NASA)
September 16 - Penumbral Lunar Eclipse
The Moon will only darken slightly during this eclipse, since it's passing through the Earth's penumbra and not full shadow, but it'll seen visible in most of eastern Europe, eastern Africa, Asia, and western Australia.
(NASA Map and Eclipse Information)
(Photo by SSPL/Getty Images)
September 22 - September Equinox
The first day of fall in the Northern Hemisphere and the first day of spring in the Southern Hemisphere brings nearly equal amounts of day and night around the world. For those who can visit China, you'll have a chance to celebrate the Mid-Autumn Festival, also known as the Moon Festival, and eat moon cakes.
(Photo by Rob Stothard/Getty Images)
October 7 - Draconids Meteor Shower
The Draconids is an unusual shower in that the best viewing is in the early evening, and it only produces 10 or so meteors an hour at its peak. Meteors will come from the constellation Draco, and you'll want to find the darkest conditions possible to watch this one.
October's full Moon will also be the first of supermoons for 2016. Supermoons occur when the Moon is both full and closest to the Earth, meaning it appears slightly larger and brighter than usual for many.
(Photo by Matt Cardy/Getty Images)
October 21, 22 - Orionids Meteor Shower
Halley's Comet left behind dust that creates the Orionids shower each year. This average shower has around 20 meteors per hour at its peak, which happens peaks this year on October 21 at night. Best viewing will be from a dark location after midnight, and look for meteors to come from the constellation Orion.
(Photo via NASA)
November 4, 5 - Taurids Meteor Shower
Although it's a relatively light meteor shower, the Taurids are unique in that they consists of two separate streams: one that comes from dust of Asteroid 2004 TG10 and another fromdebris left behind by Comet 2P Encke. The shower has an extremely long run -- from September 7 to December 10 -- and it will peak on the the night of November 4. Keep your eye on Taurus and wait for the Moon to set for the best sights.
The second "supermoon" of the year happens in November, and used to be known by early Native American tribes as the Full Beaver Moon because "this was the time of year to set the beaver traps before the swamps and rivers froze."
(AP Photo/Sergei Grits)
December 13, 14 - Geminids Meteor Shower
If you check out only one meteor shower this year, it should be the Geminids. It typically produces up to 120 multicolored meteors per hour at its peak. The shower will last from December 7 to 17, and peak on the night of the 13th. Best viewing will be from a dark location after midnight, looking to the constellation Gemini.
(Photo via TierraLady/Flickr)
December 14 - Full Moon, Supermoon
You'll be able to check out the final of three supermoons in 2016 on one of the longest nights of the year.
(AP Photo/Charlie Riedel)
December 21 - December Solstice
This is the first day of winter and longest night of the year in the Northern Hemisphere and the first day of summer and longest day of the year in the Southern Hemisphere.
(Photo by Matt Cardy/Getty Images)
December 21, 22 - Ursids Meteor Shower
This meteor shower will radiate from Ursa Minor -- also known as the little bear -- and produce about 5-10 meteors per hour.
(Photo via Shutterstock)
Discover More Like This
BACK TO SLIDE
In addition to studying the ocean, the spacecraft will collect unprecedented data of the surface.
A mission that blows others out of the water
Since 1997, the Galileo spacecraft that is orbiting Jupiter has been taking the occasional visit to Europa. But what Galileo has shown us of Europa's ice-cracked surface pales in comparison to the upcoming mission NASA has planned.
"It's going to map all of Europa at a resolution of about 25 to 50 meters," Niebur said. "It blows Galileo out of the water. Galileo maps Europa globally at about a 500-meter resolution."
Ten times better resolution is the difference between seeing cities versus parking lots, Niebur said. And it's this kind of high-res mapping that's going to get us to the surface to test the ice for signs of life.
Ultimately, it might take landing a robot on Europa, which can analyze material on the surface, to detect an alien presence. But NASA's Europa mission only involved a spacecraft that would hover over Europa — until recently.
Touching down on Europa's surface
"The challenge with any mission is always balancing cost, science return, and risk," Niebur told us. "We spent years on the flyby mission balancing those things. Now, in just the past three to six months we've been presented with the challenge of, 'Oh, could you do the same thing with a lander?'"
Leading that request is US Rep. John Culberson (R-Texas), who is the chairman of the House of Appropriations Subcommittee, with oversight of NASA's budget. For this year, Culberson helped NASA gain $175 million in funding toward its Europa mission, which was $145 million more than the agency had requested.
And he's dead-set on seeing a lander go up with the mission. In fact, in the budget legislation he ordered that the funds must be used toward a design that includes a lander, basically making it illegal to fly the mission without one, Ars Technica reported.
Niebur is not sure how much a lander will add to the $2 billion mission. And while he admits a lander would be fantastic, there's something about Europa that worries him.
"Europa is unknown territory," he said. "It's conceivable that we could get a lander close to Europa and simply never find a smooth flat place in which to land...landing on an unknown surface with unknown hazards — that keeps me up at night."
Right now, the Europa team is calculating the extra money a lander would cost to the mission. Once that's settled, NASA can move forward with construction.