NASA designs advanced new SELFI instrument to help search for life on Enceladus

The plumes of Enceladus: SELFI would study their composition in more detail than ever before. Photo Credit: NASA/JPL/Space Science Institute

Is there life on Enceladus? Are there any Enceladan bacteria or other little critters swimming in that alien ocean on this tiny moon of Saturn? We don’t know yet, but there is compelling evidence from the Cassini mission for at least a habitable environment in the dark waters below the icy crust. What’s needed now is to return to Enceladus with new and better instruments, designed especially to search for signs of active biology, which Cassini couldn’t do. Now, a new instrument has been designed by NASA which would further study the water vapour plumes erupting from the moon’s south pole and analyze what’s in them in more detail than previously possible. Those plumes are tantalizingly connected to the salty subsurface ocean below the surface ice.

The new instrument is called the Submillimeter Enceladus Life Fundamentals Instrument (SELFI) which would measure trace chemicals in the plumes. SELFI would be able to simultaneously detect and analyze 13 molecular species, including water in various isotopic forms, as well as methanol, ammonia, ozone, hydrogen peroxide, sulfur dioxide, and sodium chloride (the same salt in Earth’s oceans). These measurements would provide specific clues as to the composition and habitability of the subsurface ocean.

Diagram of an interior cross-section of the crust of Enceladus, showing how hydrothermal activity is thought to be causing the plumes of water vapour on the surface. Image Credit: NASA-GSFC/SVS/NASA/JPL-Caltech/Southwest Research Institute
Map of the Tiger Stripe fractures at the south pole of Enceladus, with plume locations marked by white circles. Cassini’s flight path during one close flyby is marked by the red line. Image Credit: NASA/JPL-Caltech/Space Science Institute

“Submillimeter wavelengths, which are in the range of very high-frequency radio, give us a way to measure the quantity of many different kinds of molecules in a cold gas. We can scan through all the plumes to see what’s coming out from Enceladus,” said SELFI Principal Investigator Gordon Chin. “Water vapour and other molecules can reveal some of the ocean’s chemistry and guide a spacecraft onto the best path to fly through the plumes to make other measurements directly.”

“Molecules such as water and carbon monoxide, and others, are like little radio stations that broadcast on very specific frequencies that say, ‘hey, I’m water, I’m carbon monoxide,’” Chin added.

“SELFI is really new,” Chin said. “This is one of the most ambitious submillimeter instruments ever built.”

Close-up view of plume activity in one of the Tiger Stripe fractures at the south pole of Enceladus. Photo Credit: NASA/JPL/Space Science Institute
Another close-up view of rough surface terrain on Enceladus. Photo Credit: NASA/JPL/Space Science Institute
A more global view of Enceladus. Photo Credit: NASA/JPL/Space Science Institute

SELFI would be much more sensitive than previous similar submillimeter instruments. With it, scientists could measure very small amounts of trace gases, even at the extremely cold temperatures of the moon’s surface, and explore the system of the surface vents themselves.

“The spectral lines are so discrete that we can identify and quantify chemicals with no confusion whatsoever,” said Paul Racette, a Goddard engineer who is the project’s chief systems engineer.

The water vapour plumes were previously analyzed by Cassini, and found to also contain ice particles, organics, carbon dioxide, methane and salts. The plumes erupt through huge cracks called Tiger Stripes in the icy surface crust, originating from a global subsurface ocean. There is also now evidence from Cassini for active hydrothermal vents on the bottom of that ocean, much like in oceans on Earth.

SELFI would be a great tool in the search for life on Enceladus (and perhaps Europa also?). Now all that’s needed is a mission to send it on.

This article was first published on AmericaSpace.

 

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A new look at ‘ocean worlds’: James Webb Space Telescope will target Europa and Enceladus

An example of possible spectroscopy results from one of Europa’s water vapour plumes. Image Credit: NASA-GSFC/SVS/Hubble Space Telescope/Stefanie Milam/Geronimo Villanueva

NASA’s upcoming James Webb Space Telescope (JWST) will be used to study two of the most fascinating moons in our Solar System  – Europa and Enceladus, also known as “ocean worlds” since both have global oceans of water beneath their outer icy surfaces. The new observations will help scientists learn more about conditions on these worlds and guide the development of future robotic missions.

Both moons are exciting targets since Europa’s surface has deposits of minerals thought to have come up from the ocean below, and Enceladus has huge plumes of water vapour erupting through fissures in the icy surface, originating from the subsurface ocean. Europa may also have plumes, which have been tentatively identified but not confirmed yet. Enceladus’ plumes also contain organic compounds of various complexities, which were sampled directly by the Cassini spacecraft multiple times.

“We chose these two moons because of their potential to exhibit chemical signatures of astrobiological interest,” said astronomer Heidi Hammel, executive vice president of the Association of Universities for Research in Astronomy (AURA).

Astronomers will use Webb’s near-infrared camera (NIRCam) to take high-resolution images of Europa’s surface, to search for hot regions related to plumes and active geological processes. If a plume is found, they can then use Webb’s near-infrared spectrograph (NIRSpec) and mid-infrared instrument (MIRI) to analyze the plume’s composition.

“Are they made of water ice? Is hot water vapour being released? What is the temperature of the active regions and the emitted water?” asked Villanueva. “Webb telescope’s measurements will allow us to address these questions with unprecedented accuracy and precision.”

JWST will be able to study Enceladus’ plumes and surface in a similar manner, even though it is about 10 times smaller than Europa as seen by the telescope.

For both moons, a focus will be to search for organic signatures such as methane, methanol, and ethane in the plumes. Evidence of life itself, like microbes, would be more difficult since some life-like processes could also have a geological explanation.

Composite image showing the possible water vapour plumes near the south pole of Europa, at about the 7 o’clock position. The image of Europa, from the Galileo and Voyager missions, is superimposed on the Hubble data. Image Credit: NASA/ESA/W. Sparks (STScI)/USGS Astrogeology Science Center
Diagram of an interior cross-section of the crust of Enceladus, showing how hydrothermal activity is thought to be causing the plumes of water vapour on the surface. Image Credit: NASA-GSFC/SVS/NASA/JPL-Caltech/Southwest Research Institute
The water vapour plumes of Enceladus, as seen by the Cassini spacecraft. Photo Credit: NASA/JPL-Caltech

“We only expect detections if the plumes are particularly active and if they are organic-rich,” Villanueva noted.

JWST is the successor to the Hubble Space Telescope (HST) and will be the most powerful space-based telescope ever built. It is an international project led by NASA, along with the European Space Agency (ESA) and the Canadian Space Agency (CSA).

Even if JWST isn’t able to find signs of life on either moon, it will be another huge step in understanding what conditions are like, both on their surfaces and below the ice in the oceans themselves, building on results from spacecraft such as Galileo and Cassini. It will help prepare the way for future, more advanced probes on the drawing boards now which may be able to answer that question of whether life has ever existed on (in) these far-off ocean worlds.

This article was first published on AmericaSpace.

 

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New findings from two ‘ocean moons’ increase possibility of finding alien life

Illustration of the Cassini spacecraft flying through the water vapour plumes of Enceladus. Image Credit: NASA/JPL-Caltech

For those who are hoping to find evidence of life somewhere else in the Solar System, there was some exciting news this week. Two moons, Europa and Enceladus, were already thought to be among the best places to search, since both have liquid water oceans beneath their outer icy shells. And now, new data from the Cassini spacecraft and the Hubble Space Telescope has increased the potential for some form of living organisms to be found.

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Enceladus’ ice-covered ocean closer to surface than previously thought

Enceladus as seen by Cassini. Photo Credit: NASA/JPL/Space Science Institute

When it comes to places in the Solar System to search for possible alien life, Saturn’s moon Enceladus is now right near the top of the list. Like Jupiter’s moon Europa, it has a subsurface ocean of water, and even plumes/geysers of water vapour which erupt from fissures in the icy surface near the south pole. Those plumes contain organics as discovered by the Cassini probe and there is evidence for hydrothermal activity on the ocean floor, just like on Earth. The fissures are warmed by heat from below, and now there is evidence that some of them are even warmer than expected, meaning that water could be closer to the surface than previously thought.

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Cassini sends back spectacular new images from first Ring-Grazing Orbit at Saturn

Saturn’s northern hemisphere up close: new image taken by Cassini on Dec. 3, 2016, showing small details in the turbulent atmosphere, including one corner of the “hexagon” with central cyclone. It was taken at a distance of about 240,000 miles (390,000 kilometers) from Saturn. Photo Credit: NASA/JPL-Caltech/Space Science Institute
Saturn’s northern hemisphere up close: new image taken by Cassini on Dec. 3, 2016, showing small details in the turbulent atmosphere, including one corner of the “hexagon” with central cyclone. It was taken at a distance of about 390,000 kilometres (240,000 miles) from Saturn. Photo Credit: NASA/JPL-Caltech/Space Science Institute

The Cassini spacecraft has successfully completed its first close pass of Saturn’s ring system, part of the Ring-Grazing Orbits phase of its mission, NASA said yesterday. As might be expected, Cassini has sent back some spectacular new images; these first images show Saturn’s northern hemisphere in incredible detail, including the famous “hexagon” jet stream surrounding the north pole.

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