Heidi Hammel Archivi - Scientificult

Webb finds carbon source on surface of Jupiter’s moon Europa

Jupiter’s moon Europa is one of a handful of worlds in our Solar System that could potentially harbour conditions suitable for life. Previous research has shown that beneath its water-ice crust lies a salty ocean of liquid water with a rocky seafloor. However, planetary scientists had not confirmed whether or not that ocean contained the chemicals needed for life, particularly carbon.

Europa (NIRCam image) — Webb’s NIRCam (Near Infrared Camera) captured this picture of the surface of Jupiter’s moon Europa. Webb identified carbon dioxide on the icy surface of Europa that likely originated in the moon’s subsurface ocean. This discovery has important implications for the potential habitability of Europa’s ocean. The moon appears mostly blue because it is brighter at shorter infrared wavelengths. The white features correspond with the chaos terrain Powys Regio (left) and Tara Regio (centre and right), which show enhanced carbon dioxide ice on the surface.
Credit:
NASA, ESA, CSA, G. Villanueva (NASA/GSFC), S. Trumbo (Cornell Univ.), A. Pagan (STScI)

Astronomers using data from the NASA/ESA/CSA James Webb Space Telescope have identified carbon dioxide in a specific region on the icy surface of Europa. Analysis indicates that this carbon likely originated in the subsurface ocean and was not delivered by meteorites or other external sources. Moreover, it was deposited on a geologically recent timescale. This discovery has important implications for the potential habitability of Europa’s ocean.

“On Earth, life likes chemical diversity — the more diversity, the better. We’re carbon-based life. Understanding the chemistry of Europa’s ocean will help us determine whether it’s hostile to life as we know it, or whether it might be a good place for life,”

said Geronimo Villanueva of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, lead author of one of two independent papers describing the findings.

“We now think that we have observational evidence that the carbon we see on Europa’s surface came from the ocean. That’s not a trivial thing. Carbon is a biologically essential element,”

added Samantha Trumbo of Cornell University in Ithaca, New York, lead author of the second paper analysing this data.

NASA plans to launch its Europa Clipper spacecraft, which will perform dozens of close flybys of Europa to further investigate whether it could have conditions suitable for life, in October 2024.

A Surface-Ocean Connection

Webb finds that on Europa’s surface, carbon dioxide is most abundant in a region called Tara Regio — a geologically young area of generally resurfaced terrain known as ‘chaos terrain’. The surface ice has been disrupted, and there has likely been an exchange of material between the subsurface ocean and the icy surface.

“Previous observations from the Hubble Space Telescope show evidence for ocean-derived salt in Tara Regio,” explained Trumbo. “Now we’re seeing that carbon dioxide is heavily concentrated there as well. We think this implies that the carbon probably has its ultimate origin in the internal ocean.”

“Scientists are debating to what extent Europa’s ocean connects to its surface. I think that question has been a big driver of Europa exploration,” said Villanueva. “This suggests that we may be able to learn some basic things about the ocean’s composition even before we drill through the ice to get the full picture.”

Both teams identified the carbon dioxide using data from the integral field unit of Webb’s Near-Infrared Spectrograph (NIRSpec). This instrument mode provides spectra with a resolution of 320 x 320 kilometres over a field of view of diameter 3128 kilometres on the surface of Europa, allowing astronomers to determine where specific chemicals are located.

Map of Europa's surface — This graphic shows a map of Europa’s surface with NIRCam (Near Infrared Camera) in the first panel and compositional maps derived from NIRSpec/IFU (Near Infrared Spectrograph’s Integral Field Unit) data in the following three panels. In the compositional maps, the white pixels correspond to carbon dioxide in the large-scale region of disrupted chaos terrain known as Tara Regio (centre and right), with additional concentrations within portions of the chaos region Powys Regio (left). The second and third panels show evidence of crystalline carbon dioxide, while the fourth panel indicates a complexed and amorphous form of carbon dioxide.
Astronomers using Webb have found carbon on the chaos terrain of Tara Regio and Powys Regio. Surface ices in these regions have been disrupted, and there has likely been a relatively recent exchange of material between the subsurface ocean and the icy surface. Carbon, a universal building block for life as we know it, likely originated in Europa’s ocean. The discovery suggests a potentially habitable environment in the salty subsurface ocean of Europa.
The NIRSpec/IFU images appear pixelated because Europa is 10 x 10 pixels across in the detector’s field of view.
Credit:
NASA, ESA, CSA, G. Villanueva (NASA/GSFC), S. Trumbo (Cornell Univ.), A. Pagan (STScI)

Carbon dioxide isn’t stable on Europa’s surface. Therefore, the scientists say it’s likely that it was supplied on a geologically recent timescale — a conclusion bolstered by its concentration in a region of young terrain.

“These observations only took a few minutes of the observatory’s time,”

said Heidi Hammel of the Association of Universities for Research in Astronomy, a Webb interdisciplinary scientist leading Webb’s Cycle 1 Guaranteed Time Observations of the Solar System.

“Even in this short period of time, we were able to do really big science. This work gives a first hint of all the amazing Solar System science we’ll be able to do with Webb.”

Searching for a Plume

Villanueva’s team also looked for evidence of a plume of water vapour erupting from Europa’s surface. Researchers using the NASA/ESA Hubble Space Telescope reported tentative detections of plumes in 2013, 2016, and 2017. However, finding definitive proof has been difficult.

The new Webb data show no evidence of plume activity, which allowed Villanueva’s team to set a strict upper limit on the rate at which material is potentially being ejected. The team stressed, however, that their non-detection does not rule out a plume.

“There is always a possibility that these plumes are variable and that you can only see them at certain times. All we can say with 100% confidence is that we did not detect a plume at Europa when we made these observations with Webb,” said Hammel.

These findings may help inform NASA’s Europa Clipper mission, as well as ESA’s Jupiter Icy Moons Explorer, Juice, which was launched on 14 April 2023. Juice will make detailed observations of the giant gas planet and its three large ocean-bearing moons — Ganymede, Callisto and Europa — with a suite of remote sensing, geophysical and in situ instruments. The mission will characterise these moons as both planetary objects and possible habitats, explore Jupiter’s complex environment in depth, and study the wider Jupiter system as an archetype for gas giants across the Universe.

“This is a great first result of what Webb will bring to the study of Jupiter’s moons,” said co-author Guillaume Cruz-Mermy, formerly of Université Paris-Saclay and current ESA Research Fellow at the European Space Astronomy Centre. “I’m looking forward to seeing what else we can learn about their surface properties from these and future observations.”

The two papers associated with this research will be published in Science on 21 September 2023.

Europa (NIRCam image, cropped) — Webb’s NIRCam (Near Infrared Camera) captured this picture of the surface of Jupiter’s moon Europa. Webb identified carbon dioxide on the icy surface of Europa that likely originated in the moon’s subsurface ocean. This discovery has important implications for the potential habitability of Europa’s ocean. The moon appears mostly blue because it is brighter at shorter infrared wavelengths. The white features correspond with the chaos terrain Powys Regio (left) and Tara Regio (centre and right), which show enhanced carbon dioxide ice on the surface.
Credit:
NASA, ESA, CSA, G. Villanueva (NASA/GSFC), S. Trumbo (Cornell Univ.), A. Pagan (STScI)

Press release from ESA Webb.

Keep Reading

Webb finds water, and a new mystery, in Comet 238P/Read, a rare main belt comet

The NASA/ESA/CSA James Webb Space Telescope has enabled another long-sought scientific breakthrough, this time for Solar System scientists studying the origins of the water that has made life on Earth possible. Using Webb’s NIRSpec (Near-Infrared Spectrograph) instrument, astronomers have confirmed gas – specifically water vapour – around a comet in the main asteroid belt for the first time, proving that water from the primordial Solar System can be preserved as ice in that region. However, the successful detection of water comes with a new puzzle: unlike other comets, Comet 238P/Read had no detectable carbon dioxide.

water Comet 238 P/Read — This artist’s concept of Comet 238P/Read shows the main belt comet sublimating—its water ice vapourising as its orbit approaches the Sun. This is significant, as the sublimation is what distinguishes comets from asteroids, creating their distinctive tail and hazy halo, or coma. The NASA/ESA/CSA James Webb Space Telescope’s detection of water vapour at Comet Read is a major benchmark in the study of main belt comets, and in the broader investigation of the origin of Earth’s abundant water.
Credit: NASA, ESA

“Our water-soaked world, teeming with life and unique in the universe as far as we know, is something of a mystery – we’re not sure how all this water got here,” said Stefanie Milam, Webb Deputy Project Scientist for Planetary Science and a co-author on the study reporting the finding. “Understanding the history of water distribution in the Solar System will help us to understand other planetary systems, and if they could be on their way to hosting an Earth-like planet,” she added.

Comet Read is a main belt comet – an object that resides in the main asteroid belt but which periodically displays a halo, or coma, and tail like a comet. Main belt comets themselves are a fairly new classification, and Comet Read was one of the original three comets used to establish the category. Before that, comets were understood to originate in the Kuiper Belt and Oort Cloud, beyond the orbit of Neptune, where their ices could be preserved farther from the Sun. Frozen material that vaporises as they approach the Sun is what gives comets their distinctive coma and streaming tail, differentiating them from asteroids. Scientists have long speculated that water ice could be preserved in the warmer asteroid belt, inside the orbit of Jupiter, but definitive proof was elusive – until Webb.

“In the past we’ve seen objects in the main belt with all the characteristics of comets, but only with this precise spectral data from Webb can we say yes, it’s definitely water ice that is creating that effect,” explained astronomer Michael Kelley of the University of Maryland, lead author of the study.

“With Webb’s observations of Comet Read, we can now demonstrate that water ice from the early Solar System can be preserved in the asteroid belt,” Kelley said.

This image of Comet 238P/Read was captured by the NIRCam (Near-Infrared Camera) instrument on the NASA/ESA/CSA James Webb Space Telescope on 8 September 2022. It displays the hazy halo, called the coma, and tail that are characteristic of comets, as opposed to asteroids. The dusty coma and tail result from the vapourisation of ices as the Sun warms the main body of the comet. Credit: NASA, ESA, CSA, M. Kelley (University of Maryland), H. Hsieh (Planetary Science Institute), A. Pagan (STScI)

The missing carbon dioxide was a bigger surprise. Typically carbon dioxide makes up about 10 percent of the volatile material in a comet that can be easily vaporised by the Sun’s heat. The science team presents two possible explanations for the lack of carbon dioxide. One possibility is that Comet Read did have carbon dioxide when it formed, but has lost that because of warm temperatures.

“Being in the asteroid belt for a long time could do it – carbon dioxide vaporises more easily than water ice, and could percolate out over billions of years,” Kelley said. Alternatively, he said, Comet Read may have formed in a particularly warm pocket of the Solar System, where no carbon dioxide was available.

The next step is taking the research beyond Comet Read to see how other main belt comets compare, says astronomer Heidi Hammel of the Association of Universities for Research in Astronomy (AURA), lead for Webb’s Guaranteed Time Observations for Solar System objects and co-author of the study.

“These objects in the asteroid belt are small and faint, and with Webb we can finally see what is going on with them and draw some conclusions. Do other main belt comets also lack carbon dioxide? Either way it will be exciting to find out,” Hammel said.

Co-author Milam imagines the possibilities of bringing the research even closer to home. “Now that Webb has confirmed there is water preserved as close as the asteroid belt, it would be fascinating to follow up on this discovery with a sample collection mission, and learn what else the main belt comets can tell us.”

The study is published in the journal Nature.

Press release from ESA Webb.

Keep Reading