It’s possible that life in our solar system is not confined to Earth. Scientists speculate that places like Mars or Enceladus could provide evidence of present or past life, but Europa has understandably gotten the most attention thanks to our wealth of knowledge about Jupiter and its moons. In a new study from NASA, scientists conclude we may not even need to dig down very deep in Europa’s ice sheet to find out whether or not it hosts life.
Scientists knew Europa was special from the very first time we got a close-up look at it. The moon, which is a little smaller than Earth’s moon, has an outer crust of water-ice that is covered with cracks. However, there are relatively few craters. That suggests the surface is active because of the presence of liquid water under the surface. The heat to keep this ocean liquid comes from the tidal flexing caused by orbiting Jupiter. There’s even some evidence the internal liquid water occasionally erupts from fissures in the surface like Enceladus.
The problem with looking for life on Europa is that we have no means to penetrate that ice sheet. NASA researchers estimate it’s at least 10-30 kilometers thick (6-19 miles), and any probe that digs down that far would have difficulty getting a signal back to Earth. The new study led by NASA’s Tom Nordheim suggests we might not need to go to such extremes to determine whether life exists on Europa.
Jupiter’s intense radiation bombards the surface of Europa, destroying any organic markers that may have migrated up from the subsurface ocean. The question you need to answer is: how deep do you have to dig before you can characterize Europa’s internal composition? If you just look at the surface, you’ll only know what Jupiter’s radiation does to Europa. Nordheim’s team constructed the most detailed model of radiation on Europa to date, which shows the most intense bands of radiation are near the equator. It turns out, we may only need to dig a few inches to get at the “real” Europa.
Water (and water-ice) is remarkably good at absorbing radiation and charged particles. Based on the calculations from Nordheim’s team, Jupiter’s radiation penetrates Europa to a depth of four to eight inches in the most irradiated zones near the equator. Near the poles, radiation only affects the top 0.4-inches of ice. The team used amino acids as a test case to determine how deep we’d need to go.
If a probe were to land on Europa and dig down past where radiation can nuke organic molecules, we have a real chance of detecting the building blocks of life. Failing to spot amino acids and similar molecules wouldn’t put an end to speculation about life on Europa, but it would make the possibility more remote. The upcoming Europa Clipper mission may be able to make passes over some of the low-radiation zones in hopes of detecting molecules that haven’t been entirely blasted by radiation.
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