New map tracks radiation levels on Europa

Map will direct future Europa missions to locations that are potentially most habitable.
By Laurel Kornfeld | Jul 24, 2018
A new map that tracks radiation bombarding Jupiter's moon Europa by its parent planet will prove an important tool in future missions searching for evidence of microbial life on the large moon.

After NASA's Galileo mission revealed the likelihood of a global ocean beneath Europa's surface, scientists have considered the Galilean moon a top contender for hosting microbial life.

Possible missions to Europa in various stage of planning seek to find biosignatures or signs of life in the underground ocean.

However, while Europa appears to be one of the solar system's best hopes for finding life, the moon is regularly bombarded by powerful radiation from Jupiter, which could reduce habitability by breaking down or destroying material transported from the ocean to the surface.

Now, a new study led by Tom Nordheim of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, has produced the most comprehensive map ever of radiation levels on Europa using data returned by the Galileo mission's flybys of Europa 20 years ago and electron measurements returned by Voyager 1, which flew by the Jupiter system in early 1979.

From the data returned by these missions, Nordheim's team found radiation levels on Europa to vary significantly depending on location, with the highest radiation levels found near the equator and the lowest levels found near the poles.

The researchers produced a map that depicts high radiation zones as ovals.

"This is our first prediction of radiation levels at each point on Europa's surface and is important information for future Europa missions," noted Chris Paranicas of the Johns Hopkins Applied Physics Laboratory (JHUAPL) in Laurel, Maryland, who took part in the study.

"If we want to understand what's going on at the surface of Europa and how that links to the ocean underneath, we need to understand the radiation," Nordheim emphasized. "When we examine materials that have come up from the subsurface, what are we looking at? Does this tell us what is in the ocean, or is this what happened to the materials after they have been radiated?"

Nordheim's research team also measured how deeply radiation from Jupiter penetrates beneath Europa's surface, providing important information for the Europa Clipper mission, which will conduct about 45 Europa flybys while orbiting Jupiter following an early 2020s launch.

They found that in the regions with the highest radiation levels, a probe would have to drill four to eight inches (10 to 20 cm) to find preserved biosignatures. In those with the lowest radiation levels, the probe would have to drill less than 0.4 inches (one cm).

A paper on the study has been published in the journal Nature Astronomy.

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