Hello again. Last time out, we took a brief look at one avenue where scientists at NASA are concentrating their efforts to help broaden our understanding of the origins of life, and where else it might be found. In particular, we dipped our toes into those oceans we’ve found beyond Earth within our solar system.
As promised, this time around we’ll take a more in-depth look at just two of the prime candidates in particular. Why only two? Because NASA has accumulated evidence that that tends to prove the most likely places to find life beyond Earth are Jupiter’s moon Europa, or Saturn’s moon Enceladus.
Here are some of the details regarding Enceladus:
Saturn’s sixth-largest moon is a frost-encased world with a large ocean lying beneath a frigid rind. Using a mass spectrometer, the Cassini spacecraft detected an abundance of hydrogen molecules in water plumes rising from the “tiger stripe” fractures in Enceladus’ icy surface. Researchers believe that the hydrogen originates from a hydrothermal reaction between the satellite’s ocean and its rocky core. If this is the case, then methane could be forming in the ocean as well, and that chemical is crucial for life.
“Enceladus is high on the list in the solar system for showing habitable conditions,” said Hunter Waite, leader of the Cassini Ion and Neutral Mass Spectrometer team at the Southwest Research Institute in San Antonio and lead author of the Enceladus study. “The presence of hydrogen established another reference point saying there is hydrothermal activity inside this body, and that’s interesting because we know in our own oceans, those are very important places that are teeming with life, and they are probably one of the earliest places where life happened on Earth.”
What about Europa?
The Hubble Space Telescope showed water plumes erupting on the warmest part of the surface of Europa, a moon of Jupiter that also possess an icy crust over a salty liquid water ocean. What I found interesting is that Europa’s ocean contains twice as much water as the Earth’s seas. This is the second time a plume has been observed in this exact spot, which has researchers excited that it could prove to be a feature on the surface.
“This is significant, because the rest of the planet isn’t easy to predict or understand, and it’s happening for the second time in the warmest spot,” said Britney Schmidt, second author on the Europa study and assistant professor at the Georgia Institute of Technology’s School of Earth and Atmospheric Sciences.
Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate, added, “This is the closest we’ve come, so far, to identifying a place with some of the ingredients needed for a habitable environment. These results demonstrate the interconnected nature of NASA’s science missions that are getting us closer to answering whether we are indeed alone or not.”
The necessary ingredients for life as we know it include liquid water; an energy source; and chemicals such as carbon, hydrogen, oxygen, nitrogen, sulfur and phosphorus.
And as we’ve learned here on Earth, life finds a way to exist in the harshest of environments. In vents in the deepest parts of the ocean floor, for example, are microbes that don’t receive energy from sunlight. Instead, they use methanogenesis, a process that reduces carbon dioxide with hydrogen, to form methane.
Europa and Enceladus are showcasing some of these key ingredients for life in their oceans, which is why researchers believe they are the best chance for finding life beyond Earth in our own solar system.
Of note is that previous results from the Cassini mission’s flybys of Enceladus tick many of the right boxes. One, they see plume material linked to interior water; two, the moon has a global ocean; and since then, a cosmic dust analyzer has revealed silicon dioxide grains, indicating warm hydrothermal activity.
“This (molecular hydrogen) is just like the icing on the cake,” Waite – mentioned earlier – said. “Now, you see the chemical energy source that microbes could use. The only thing we haven’t seen is phosphorus and sulfur, and that’s probably because they were in small enough quantities that we didn’t see them. We have to go back and look and search for signs of life as well.”
Although the Cassini mission, which began in 2004, comes to an end this year, Waite is eager for NASA to return to Enceladus because he believes it is the best candidate.
Researchers want to confirm a solid case for habitability by finding sulfur and phosphorus on Enceladus, as well as reinforcing previous measurements. The next steps would be to look for signs of life by flying a spectrometer through the plume; searching for rations of amino and fatty acids; and testing for certain isotopic ratios indicative of life.
However, it looks as if Waite is going to have to be patient, because NASA is gearing up to face Europa first via the recently named Europa Clipper mission. (the first to explore an alien ocean).
The Europa Clipper, named for the innovative, streamlined ships of the 1800s, will launch in the 2020s and arrive at Europa after a few years.
“The reason we chose it is because the clipper ships were fast, American boats at the time that they were first used, when most shipping was achieved with large, slow vessels,” Said Britney Schmidt. “We liked clipper for that reason, an ingenious way to solve the Europa mission problem: How do you get a long-lived mission at Europa with global coverage but not be in the radiation environment?”
Because that region of the solar system traps atomic particles from the sun, the radiation of the area around Jupiter is dangerous to spacecraft.
Schmidt will be an investigator for the ice-penetrating radar instrument that will be housed on the Europa Clipper. Acting like an X-ray, it will peer down through the unknown thickness of Europa’s icy crust and assess what’s going on inside that faraway little world.
Europa or Enceladus?
Research suggesting the possibility of an ocean on Europa was first published as early as 1977, after the Voyager mission saw long lines and dark spots, as opposed to a cratered surface similar to other moons. Then the Galileo mission reached Europa in 1996 and revealed for the first time that there was an ocean on another planet.
The trouble is our much closer neighbor, Mars, has fueled the imagination of extra planetary exploration for generations. As such, the general public isn’t as enthralled by the thought of doing the same with a moon elsewhere. But think about that for a moment. Increasing evidence tends to suggest life might have existed on Mars in the past, at a time when it was capable of supporting bodies of water and had a more hospitable climate and atmosphere than it does now.
“The question is, do you want to study something that might have been habitable at one time, or do you want to study something that could be habitable right now?” Schmidt asked. “Europa has been pretty much Europa for 4.5 billion years, as long as the Earth has. So as far as what could have started and evolved there, that’s a compelling question.
“If you think about early Earth and early Europa, they were probably very similar, at least at the ocean interface. They are almost the same place at that point in time. That’s why I get excited about Europa. It could have been a place for life over the history of the solar system.”
Regardless of which of the two ocean worlds is the better candidate for hosting life, both researchers believe that exploring ocean worlds is one of the best things we can do, as understanding the diversity within our own solar system will extend our expectations and help us prepare for future colonization projects.
As we mentioned last time out, the threshold to “Infinity and beyond” might soon lie within our grasp. How soon?
Join in next time when we take a more detailed look at some of the other diverse projects NASA is currently developing that all tie together in the greater name of space exploration. You won’t believe how “mundane” some of them sound… ☺
See you then.