- Europa is an icy moon of Jupiter that harbours an ocean and might support alien life.
- Despite several flyby missions of Europa, no full geologic map of the moon previously existed.
- Scientists released the first map in October after roughly 15 years of effort.
- The map will help NASA pick targets for its upcoming Europa Clipper mission and possibly a Europa Lander mission.
NASA is gearing up to spend billions answering one of the most significant questions humans have ever posed: Are we alone?
One of the space agency’s prime targets for seeking evidence of alien life is Europa, an icy satellite of Jupiter that’s nearly the size of our own moon yet hides an ocean thought to contain more liquid water than exists on Earth.
But before NASA can send its first Europa-dedicated mission — the Europa Clipper, a solar-powered robot that will repeatedly strafe the moon with cameras and sensitive scientific instruments — the space agency needs a map of the mysterious world to make the most of its $US2-to-$US4 billion effort.
Now this map exists, thanks to the determination of two groups of researchers spanning more than a decade.
“There was never a completed global map prior to ours,” D. Alex Patthoff, a geologist and planetary scientist at NASA’s Jet Propulsion Laboratory, told Business Insider in an email.
Business Insider first learned about the research project via a story at AGU Eos by writer JoAnna Wendel.
Mapping an alien ice ball
Europa is a promising destination not only because of its ocean, but for the potential of those warm, salty waters to host extraterrestrial life.
Its surface is also scarred with fissures and relatively free of craters, suggesting oxygen- and nutrient-laden ice regularly sinks into the waters below. There’s even limited evidence that Europa sprays plumes of water into space.
However, no dedicated mission has ever studied the moon in great detail — including its unexplored north and south poles. “This is another reason we need to go back and take a closer look at Europa,” Patthoff said.
Anticipating future exploration of Europa, planetary scientist Ron Greeley began painstakingly piecing together all of the available images into an unprecedented geologic map of Europa in the early 2000s.
But Greeley passed away in October 2011 before finishing the map.
“The Europa Clipper mission was the inspiration to complete the Global Geologic map,” Leonard told Business Insider in an email. “The project will use it for mission planning, for instance knowing what features that might be observed on a particular flyby of Europa.”
Its use will likely extend to the Europa Lander robot: a roughly $US4 billion follow-up mission championed by Republican congressman John Culberson.
Such a robot could reach the giant ice ball’s surface in the 2030s, if NASA gets the funding it needs.
“The map could be used as a launching off point for finding an area of interest for landing, especially if they are interested in a certain collection of features, such as ‘bands’ or ‘microchaos,'” Leonard said.
Chaotic terrain to explore
The researchers said it took so long to piece the map together because of the wildly varying image sources, distances, and lighting.
For example, data from Galileo — a mission that arrived at Jupiter in 1995, and the richest source of imagery — came from 11 different flybys of Europa spread over nearly eight years.
“Sometimes the light is coming from directly overhead, essentially noon, while other it is lower on the horizon, late afternoon. This can make the shadows and the colour of the surface vary from image to image,” Patthoff said. “It can be like trying to map the US where in only a few images you could see something the size of the White House, while in most other images you could discern only cities such as New York City or San Francisco.”
The new map pieces together seemingly disparate features and unmasks Europa’s complex geology. Patthoff, Leonard, and their colleagues David Senske and Geoffrey C. Collins labelled 18 different types of features and terrain that future missions to Europa may want to target.
The youngest terrain — liquid water that most recently froze into ice — is known as “chaos” terrain (green colours) because of its slapdash grouping of ice rafts, some of which are roughly the size of San Francisco.
Bands (purples) are also relatively young, the researchers say, since they appear to cut across older material like ridged plains (blues). Craters and the materials they eject into the surroundings are also marked (oranges).
No one knows just how “young” Europa’s icy crust is on average — estimates range from 10 million to 100 million years. However, researchers believe ice melt happens frequently enough for oxygen on the surface (created by Jupiter’s intense radiation field) to cycle into the ocean and support life.
The next step is to look into all of the other materials there, including sulphur spewed out by volcanoes on Jupiter’s moon Io, and estimate just how frequently they move into the ocean.
“A decade or so ago, we had no idea there might be several global oceans within our solar system. Now that’s becoming generally accepted. So, satellite oceans may be the most common habitats for life that exist in the universe,” Bob Pappalardo, a planetary scientist at NASA JPL, previously told Business Insider.
“Then the question is, could these oceans generally support life?” he added. “That’s the goal of the Europa Clipper mission. We need to understand [the] prospect for chemicals getting into the ocean … and from the interior.”
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