Hubble finds water vapour in the atmosphere of GJ 9827d, a small exoplanet
Astronomers using the NASA/ESA Hubble Space Telescope observed the smallest exoplanet where water vapour has been detected in its atmosphere, GJ 9827d. At only approximately twice Earth’s diameter, the planet GJ 9827d could be an example of potential planets with water-rich atmospheres elsewhere in our galaxy.
“This would be the first time that we can directly show through an atmospheric detection that these planets with water-rich atmospheres can actually exist around other stars,” said team member Björn Benneke of the Université de Montréal. “This is an important step toward determining the prevalence and diversity of atmospheres on rocky planets.”
However, it remains too early to tell whether Hubble spectroscopically measured a small amount of water vapour in a puffy hydrogen-rich atmosphere, or if the planet’s atmosphere is mostly made of water, left behind after a primaeval hydrogen/helium atmosphere evapourated under stellar radiation.
“Our observing programme was designed specifically with the goal of not only detecting the molecules in the planet’s atmosphere, but of actually looking specifically for water vapour. Either result would be exciting, whether water vapour is dominant or just a tiny species in a hydrogen-dominant atmosphere,” said the science paper’s lead author, Pierre-Alexis Roy of the Université de Montréal.
“Until now, we had not been able to directly detect the atmosphere of such a small planet. And we’re slowly getting into this regime now,” added Benneke. “At some point, as we study smaller planets, there must be a transition where there’s no more hydrogen on these small worlds, and they have atmospheres more like Venus (which is dominated by carbon dioxide).”
Because the planet is as hot as Venus at roughly 425 degrees Celsius, it definitely would be an inhospitable, steamy world if the atmosphere were predominantly water vapour.
At present the team is left with two possibilities. The planet is still clinging to a hydrogen-rich envelope laced with water, making it a mini-Neptune. Alternatively, it could be a warmer version of Jupiter’s moon Europa, which has twice as much water as Earth beneath its crust.
“The planet GJ 9827d could be half water, half rock. And there would be a lot of water vapour on top of some smaller rocky body,” said Benneke.
If the planet has a residual water-rich atmosphere, then it must have formed farther away from its host star, where the temperature is cold and water is available in the form of ice, than its present location. In this scenario, the planet would have then migrated closer to the star and received more radiation. The hydrogen was then heated and escaped, or is still in the process of escaping, the planet’s weak gravity. The alternative theory is that the planet formed close to the hot star, with a trace of water in its atmosphere.
The Hubble programme observed the planet during 11 transits — events in which the planet crossed in front of its star — that were spaced out over three years. During transits, starlight is filtered through the planet’s atmosphere and carries the spectral fingerprint of water molecules. If there are clouds on the planet, they are low enough in the atmosphere that they don’t completely hide Hubble’s view of the atmosphere, and Hubble is able to probe water vapour above the clouds.
Hubble’s discovery opens the door to studying the planet in more detail. It’s a good target for the NASA/ESA/CSA James Webb Space Telescope to do infrared spectroscopy to look for other atmospheric molecules.
GJ 9827d was discovered by NASA’s Kepler Space Telescope in 2017. It completes an orbit around a red dwarf star every 6.2 days. The star, GJ 9827, lies 97 light-years from Earth in the constellation Pisces.
This is an artist’s conception of the exoplanet GJ 9827d, the smallest exoplanet where water vapour has been detected in its atmosphere. The planet could be an example of potential planets with water-rich atmospheres elsewhere in our galaxy. It is a rocky world, only about twice Earth’s diameter. It orbits the red dwarf star GJ 9827. Two inner planets in the system are on the left. The background stars are plotted as they would be seen to the unaided eye looking back toward our Sun, which itself is too faint to be seen. The blue star at upper right is Regulus, the yellow star at bottom centre is Denebola, and the blue star at bottom right is Spica. The constellation Leo is on the left, and Virgo is on the right. Both constellations are distorted from our Earth-bound view from 97 light-years away. Credit: NASA, ESA, Leah Hustak and Ralf Crawford (STScI)
The protoplanetary disc XUE 1 shows that rocky planets can form in extreme environments; the study has been published in The Astrophysical Journal
An international team of astronomers have used the NASA/ESA/CSA James Webb Space Telescope to provide the first observation of water and other molecules in the inner, rocky-planet-forming regions of a disc in one of the most extreme environments in our Galaxy. These results suggest that the conditions for rocky-planet formation, typically found in the discs of low-mass star-forming regions, can also occur in massive-star-forming regions and possibly a broader range of environments.
This is an artist’s impression of a young star surrounded by a protoplanetary disc in which planets are forming. An international team of astronomers have used the NASA/ESA/CSA James Webb Space Telescope to provide the first observation of water and other molecules in the inner, rocky-planet-forming regions of a disc in one of the most extreme environments in our galaxy. These results suggest that the conditions for rocky-planet formation, typically found in the discs of low-mass star-forming regions, can also occur in massive-star-forming regions and possibly a broader range of environments. Credit: ESO/L. Calçada
These are the first results from the eXtreme UV Environments (XUE) James Webb Space Telescope programme, that focuses on the characterisation of planet-forming disc in massive-star-forming regions. These regions are likely representative of the environment in which most planetary systems formed. Understanding the impact of environment on planet formation is important for scientists to gain insights into the diversity of the observed exoplanet populations.
The XUE programme targets a total of 15 discs in three areas of the Lobster Nebula (also known as NGC 6357), a large emission nebula roughly 5500 light-years away from Earth in the constellation Scorpius. The Lobster Nebula is one of the youngest and closest massive star formation complexes, and is host to some of the most massive stars in our Galaxy. Massive stars are hotter, and therefore emit more ultraviolet (UV) radiation. This can disperse the gas, making the expected disc lifetime as short as a million years. Thanks to Webb, astronomers can now study the effect of UV radiation on the inner rocky-planet-forming regions of protoplanetary discs around stars like our Sun.
“Webb is the only telescope with the spatial resolution and sensitivity to study planet-forming discs in massive-star-forming regions,” said team lead María Claudia Ramírez-Tannus of the Max Planck Institute for Astronomy in Germany.
Astronomers aim to characterise the physical properties and chemical composition of the rocky-planet-forming regions of discs in the Lobster Nebula using Webb’s Medium Resolution Spectrometer (MRS) of the Mid-InfraRed Instrument (MIRI). This first result focuses on the protoplanetary disc termed XUE 1, which is located in the star cluster Pismis 24.
This graphic presents some of the first results from the eXtreme UV Environments (XUE) James Webb Space Telescope programme. These results suggest that the conditions for rocky-planet formation, typically found in the discs of low-mass star-forming regions, can also occur in massive-star-forming regions and possibly a broader range of environments. Astronomers focussed on rocky-planet-forming regions of discs in the Lobster Nebula using Webb’s Medium Resolution Spectrometer (MRS) of the Mid-InfraRed Instrument (MIRI). This first result focuses on the protoplanetary disc termed XUE 1, which is located in the star cluster Pismis 24. This graphic features the observed signatures of carbon monoxide spanning 4.95 to 5.15 microns Credit: NASA, ESA, CSA, STScI, J. Olmsted (STScI), M. C Ramírez-Tannus (Max Planck Institute for Astronomy)This graphic presents some of the first results from the eXtreme UV Environments (XUE) James Webb Space Telescope programme. These results suggest that the conditions for rocky-planet formation, typically found in the discs of low-mass star-forming regions, can also occur in massive-star-forming regions and possibly a broader range of environments. Astronomers focussed on rocky-planet-forming regions of discs in the Lobster Nebula using Webb’s Medium Resolution Spectrometer (MRS) of the Mid-InfraRed Instrument (MIRI). This first result focuses on the protoplanetary disc termed XUE 1, which is located in the star cluster Pismis 24. The inner disc around XUE 1 revealed signatures of water (highlighted here in blue and centred around 14.2 microns), as well as acetylene (C2H2, highlighted in green; centred around 13.7 microns), hydrogen cyanide (HCN, highlighted in brown; centred around 14.0 microns), and carbon dioxide (CO2, highlighted in red; centred around 14.95 microns). As indicated, some of the emission detected was weaker than some of the predicted models, which might imply a small outer disc radius. Credit: NASA, ESA, CSA, STScI, J. Olmsted (STScI), M. C Ramírez-Tannus (Max Planck Institute for Astronomy)
“Only the MIRI wavelength range and spectral resolution allow us to probe the molecular inventory and physical conditions of the warm gas and dust where rocky planets form,” said team member Arjan Bik of Stockholm University in Sweden.
Because of its location near several massive stars in NGC6357, scientists expect XUE 1 to have been constantly exposed to a high ultraviolet radiation field throughout its life. However, in this extreme environment the team still detected a range of molecules that are the building blocks of rocky planets.
“We find that the inner disk around XUE 1 is remarkably similar to those in nearby star-forming regions,” said team member Rens Waters of Radboud University in the Netherlands. “We’ve detected water and other molecules like carbon monoxide, carbon dioxide, hydrogen cyanide and acetylene. However, the emission found was weaker than some models predicted. This might imply a small outer disc radius.”
“We were surprised and excited because this is the first time that these molecules have been detected under such extreme conditions,” added Lars Cuijpers of Radboud University. The team also found small, partially crystalline silicate dust at the disc’s surface. This is considered to be the building blocks of rocky planets.
These results are good news for rocky planet formation, as the science team finds that the conditions in the inner disc resemble those found in the well-studied disks located in nearby star-forming regions, where only low-mass stars form. This suggests that rocky planets can form in a much broader range of environments than previously believed.
The team notes that the remaining observations from the XUE programme are crucial to establishing the commonality of these conditions.
“XUE1 shows us that the conditions to form rocky planets are there, so the next step is to check how common that is,” says Ramírez-Tannus. “We will observe other discs in the same region to determine the frequency with which these conditions can be observed.”
These results have been published in The Astrophysical Journal.
Webb detects water vapour in the inner disk of the system PDS 70, a rocky planet-forming zone
New measurements by the NASA/ESA/CSA James Webb Space Telescope’s Mid-InfraRed Instrument (MIRI) have detected water vapour in the inner disc of the system PDS 70, located 370 light-years away. This is the first detection of water in the terrestrial region of a disc already known to host two or more protoplanets.
This artist concept portrays the star PDS 70 and its inner protoplanetary disc. New measurements from the NASA/ESA/CSA James Webb Space Telescope’s Mid-InfraRed Instrument (MIRI) have indicated the presence of water vapour in the inner disc of the system PDS 70, located 370 light-years away. This is the first detection of water in the terrestrial region of a disc already known to host two or more protoplanets, one of which is shown at upper right. Credit: NASA, ESA, CSA, J. Olmsted (STScI)
Water is essential for life as we know it. However, scientists debate how it reached the Earth and whether the same processes could seed rocky exoplanets orbiting distant stars. New insights may come from the system PDS 70, which hosts an inner disc and an outer disc that are separated by a gap of eight billion kilometres, within which are two known gas-giant planets. MIRI has detected water vapour in the system’s inner disc at distances of less than 160 million kilometres from the star — the region where rocky, terrestrial planets may be forming (the Earth orbits 150 million kilometres from our Sun).
“We’ve seen water in other discs, but not so close in and in a system where planets are currently assembling. We couldn’t make this type of measurement before Webb,” said lead author Giulia Perotti of the Max Planck Institute for Astronomy (MPIA) in Heidelberg, Germany.
“This discovery is extremely exciting, as it probes the region where rocky planets similar to Earth typically form,”
added MPIA director Thomas Henning, a co-author of the paper. Henning is co-principal investigator of Webb’s MIRI (Mid-InfraRed Instrument), which made the detection, and the principal investigator of the MINDS (MIRI Mid-Infrared Disk Survey) programme that took the data.
A wet environment for forming planets
PDS 70 is a K-type star, cooler than our Sun, and is estimated to be 5.4 million years old. This is relatively old amongst stars with planet-forming discs, which made the discovery of water vapour surprising.
Over time, the gas and dust content of planet-forming discs declines. Either the central star’s radiation and winds remove such material, or the dust grows into larger objects that eventually form planets. As previous studies failed to detect water in the central regions of similarly aged discs, astronomers suspected it might not survive the harsh stellar radiation, leading to a dry environment for the formation of any rocky planets.
Astronomers haven’t yet detected any planets forming within the inner disc of PDS 70. However, they do see the raw materials for building rocky worlds, in the form of silicates. The detection of water vapour implies that if rocky planets are forming there, they will have water available to them from the beginning.
“We find a relatively large amount of small dust grains. Combined with our detection of water vapour, the inner disc is a very exciting place,” said co-author Rens Waters of Radboud University in the Netherlands.
What is the origin of the water?
The discovery raises the question of where the water came from. The MINDS team considered two different scenarios to explain their finding.
One possibility is that water molecules are forming in place, where we detect them, as hydrogen and oxygen atoms combine. A second possibility is that ice-coated dust particles are being transported from the cool outer disc to the hot inner disc, where the water ice sublimates and turns into vapour. Such a transport system would be surprising, since the dust would have to cross the large gap carved out by the two giant planets.
Another question raised by the discovery is how water could survive so close to the star, where the star’s ultraviolet light should break apart any water molecules. Most likely, surrounding material, such as dust and other water molecules, serves as a protective shield. As a result, the water detected near PDS 70 could survive destruction.
Ultimately, the team will use two of Webb’s other instruments, the Near-InfraRed Camera (NIRCam) and the Near-InfraRed Spectrograph (NIRSpec) to study the PDS 70 system in an effort to glean an even greater understanding.
These observations were made as part of Guaranteed Time Observation program 1282. This finding has been published in the journal Nature.
New measurements from the NASA/ESA/CSA James Webb Space Telescope’s Mid-InfraRed Instrument (MIRI) have indicated the presence of water vapour in the inner disc of the system PDS 70, located 370 light-years away. This is the first detection of water in the terrestrial region of a disc already known to host two or more protoplanets. This spectrum of the protoplanetary disk of PDS 70, obtained with Webb’s MIRI instrument, displays a number of emission lines from water vapour. Credit: NASA, ESA, CSA, J. Olmsted (STScI)
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.
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.
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 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.”
This graphic presentation of spectral data highlights a key similarity and difference between observations of Comet 238P/Read by the NIRSpec (Near-Infrared Spectrograph) instrument on the NASA/ESA/CSA James Webb Space Telescope in 2022 and observations of Comet 103P/Hartley 2 by NASA’s Deep Impact mission in 2010. Both show a distinct peak in the region of the spectrum associated with water. Finding this in Comet Read was a significant accomplishment for Webb, as it is in a different class of comets than Jupiter-family comets like Hartley 2, and this marks the first time that a gas has been confirmed in such a main belt comet. However, Comet Read did not show the characteristic, expected bump indicating the presence of carbon dioxide. Credit: NASA, ESA, CSA, and J. Olmsted (STScI)
Webb spots swirling, gritty clouds on VHS 1256 b, a remote planet
Researchers observing with the NASA/ESA/CSA James Webb Space Telescope have pinpointed silicate cloud features in a distant planet’s atmosphere. The atmosphere is constantly rising, mixing, and moving during its 22-hour day, bringing hotter material up and pushing colder material down. The resulting brightness changes are so dramatic that it is the most variable planetary-mass object known to date. The science team also made extraordinarily clear detections of water, methane and carbon monoxide with Webb’s data, and found evidence of carbon dioxide. This is the largest number of molecules ever identified all at once on a planet outside our Solar System.
This illustration conceptualises the swirling clouds identified by the James Webb Space Telescope in the atmosphere of the exoplanet VHS 1256 b. The planet is about 40 light-years away and orbits two stars that are locked in their own tight rotation. Its clouds, which are filled with silicate dust, are constantly rising, mixing, and moving during its 22-hour day. Credit: NASA, ESA, CSA, J. Olmsted (STScI)
Catalogued as VHS 1256 b, the planet is about 40 light-years away and orbits not one, but two stars over a 10 000-year period.
“VHS 1256 b is about four times farther from its stars than Pluto is from our Sun, which makes it a great target for Webb,” said science team lead Brittany Miles of the University of Arizona. “That means the planet’s light is not mixed with light from its stars.” Higher up in its atmosphere, where the silicate clouds are churning, temperatures reach a scorching 830 degrees Celsius.
Within those clouds, Webb detected both larger and smaller silicate dust grains, which are shown on a spectrum.
“The finer silicate grains in its atmosphere may be more like tiny particles in smoke,” noted co-author Beth Biller of the University of Edinburgh in the United Kingdom. “The larger grains might be more like very hot, very small sand particles.”
VHS 1256 b has low gravity compared to more massive brown dwarfs [1], which means that its silicate clouds can appear and remain higher in its atmosphere where Webb can detect them. Another reason its skies are so turbulent is the planet’s age. In astronomical terms, it’s quite young. Only 150 million years have passed since it formed — and it will continue to change and cool over billions of years.
A research team led by Brittany Miles of the University of Arizona used two instruments known as spectrographs aboard the James Webb Space Telescope, one on its Near Infrared Spectrograph (NIRSpec) and another on its Mid-Infrared Instrument (MIRI), to observe a vast section of near- to mid-infrared light emitted by the planet VHS 1256 b. They plotted the light on the spectrum, identifying signatures of silicate clouds, water, methane and carbon monoxide. They also found evidence of carbon dioxide. Credit: NASA, ESA, CSA, J. Olmsted (STScI), B. Miles (University of Arizona), S. Hinkley (University of Exeter), B. Biller (University of Edinburgh), A. Skemer (University of California, Santa Cruz)
In many ways, the team considers these findings to be the first ‘coins’ pulled out of a spectrum that researchers view as a treasure chest of data. In many ways, they’ve only begun identifying its contents.
“We’ve identified silicates, but a better understanding of which grain sizes and shapes match specific types of clouds is going to take a lot of additional work,” Miles said. “This is not the final word on this planet — it is the beginning of a large-scale modelling effort to fit Webb’s complex data.”
Although all of the features the team observed have been spotted on other planets elsewhere in the Milky Way by other telescopes, other research teams typically identified only one at a time.
“No other telescope has identified so many features at once for a single target,” said co-author Andrew Skemer of the University of California, Santa Cruz. “We’re seeing a lot of molecules in a single spectrum from Webb that detail the planet’s dynamic cloud and weather systems.”
The team came to these conclusions by analysing data known as spectra gathered by two instruments aboard Webb, the Near-Infrared Spectrograph (NIRSpec) and the Mid-Infrared Instrument (MIRI). Since the planet orbits at such a great distance from its stars, the researchers were able to observe it directly, rather than using the transit technique [2] or a coronagraph [3] to take this data.
There will be plenty more to learn about VHS 1256 b in the months and years to come as this team — and others — continue to sift through Webb’s high-resolution infrared data. “There’s a huge return on a very modest amount of telescope time,” Biller added. “With only a few hours of observations, we have what feels like unending potential for additional discoveries.”
What might become of this planet billions of years from now? Since it’s so far from its stars, it will become colder over time, and its skies may transition from cloudy to clear.
The researchers observed VHS 1256 b as part of Webb’s Early Release Science program, which is designed to help transform the astronomical community’s ability to characterise planets and the discs from which they form.
The team’s paper, entitled “The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems II: A 1 to 20 Micron Spectrum of the Planetary-Mass Companion VHS 1256-1257 b,” will be published in The Astrophysical Journal Letters on 22 March.
Webb Unveils Dark Side of Pre-stellar Ice Chemistry
The discovery of diverse ices in the darkest, coldest regions of a molecular cloud measured to date has been announced by an international team of astronomers using the NASA/ESA/CSA James Webb Space Telescope. This result allows astronomers to examine the simple icy molecules that will be incorporated into future exoplanets, while opening a new window on the origin of more complex molecules that are the first step in the creation of the building blocks of life.
This image by the NASA/ESA/CSA James Webb Space Telescope’s Near-InfraRed Camera (NIRCam) features the central region of the Chameleon I dark molecular cloud, which resides 630 light years away. The cold, wispy cloud material (blue, centre) is illuminated in the infrared by the glow of the young, outflowing protostar Ced 110 IRS 4 (orange, upper left). The light from numerous background stars, seen as orange dots behind the cloud, can be used to detect ices in the cloud, which absorb the starlight passing through them. An international team of astronomers has reported the discovery of diverse ices in the darkest, coldest regions of a molecular cloud measured to date by studying this region. This result allows astronomers to examine the simple icy molecules that will be incorporated into future exoplanets, while opening a new window on the origin of more complex molecules that are the first step in the creation of the building blocks of life. Credit: NASA, ESA, CSA, and M. Zamani (ESA/Webb); Science: F. Sun (Steward Observatory), Z. Smith (Open University), and the Ice Age ERS Team
If you want to build a habitable planet, ices are a vital ingredient as they are the main carriers of several key light elements — namely carbon, hydrogen, oxygen, nitrogen, and sulphur (referred to collectively as CHONS). These elements are important ingredients in both planetary atmospheres and molecules like sugars, alcohols, and simple amino acids. In our Solar System, it is thought they were delivered to Earth’s surface by impacts with icy comets or asteroids. Furthermore, astronomers believe such ices were most likely already present in the dark cloud of cold dust and gas that would eventually collapse to make the Solar System. In these regions of space, icy dust grains provide a unique setting for atoms and molecules to meet, which can trigger chemical reactions that form very common substances like water. Detailed laboratory studies have further shown that some simple prebiotic molecules can form under these icy conditions.
Now an in-depth inventory of the deepest, coldest ices measured to date in a molecular cloud [1] has been announced by an international team of astronomers using the NASA/ESA/CSA James Webb Space Telescope. In addition to simple ices like water, the team was able to identify frozen forms of a wide range of molecules, from carbonyl sulfide, ammonia, and methane, to the simplest complex organic molecule, methanol (in the interstellar medium, organic molecules are considered to be complex when having six or more atoms). This is the most comprehensive census to date of the icy ingredients available to make future generations of stars and planets, before they are heated during the formation of young stars. These icy grains grow in size as they are funnelled into the protoplanetary discs of gas and dust around these young stars, essentially allowing astronomers to study all the potential icy molecules that will be incorporated into future exoplanets.
“Our results provide insights into the initial, dark chemistry stage of the formation of ice on the interstellar dust grains that will grow into the centimetre-sized pebbles from which planets form in discs,” said Melissa McClure, an astronomer at Leiden Observatory who is the principal investigator of the observing program and lead author of the paper describing this result. “These observations open a new window on the formation pathways for the simple and complex molecules that are needed to make the building blocks of life.”
In addition to the identified molecules, the team found evidence for prebiotic molecules more complex than methanol in these dense cloud ices, and, although they didn’t definitively attribute these signals to specific molecules, this proves for the first time that complex molecules form in the icy depths of molecular clouds before stars are born.
“Our identification of complex organic molecules, like methanol and potentially ethanol, also suggests that the many star and planet systems developing in this particular cloud will inherit molecules in a fairly advanced chemical state,” added Will Rocha, an astronomer at Leiden Observatory who contributed to this discovery. “This could mean that the presence of prebiotic molecules in planetary systems is a common result of star formation, rather than a unique feature of our own Solar System.”
By detecting the sulfur-bearing ice carbonyl sulfide, the researchers were able to estimate the amount of sulfur embedded in icy pre-stellar dust grains for the first time. While the amount measured is larger than previously observed, it is still less than the total amount expected to be present in this cloud, based on its density. This is true for the other CHONS elements as well. A key challenge for astronomers is understanding where these elements are hiding: in ices, soot-like materials, or rocks. The amount of CHONS in each type of material determines how much of these elements end up in exoplanet atmospheres and how much in their interiors.
“The fact that we haven’t seen all of the CHONS that we expect may indicate that they are locked up in more rocky or sooty materials that we cannot measure,” explained McClure. “This could allow a greater diversity in the bulk composition of terrestrial planets.”
Webb Unveils Dark Side of Pre-stellar Ice Chemistry. Astronomers have taken an inventory of the most deeply embedded ices in a cold molecular cloud to date. They used light from a background star, named NIR38, to illuminate the dark cloud called Chameleon I. Ices within the cloud absorbed certain wavelengths of infrared light, leaving spectral fingerprints called absorption lines. These lines indicate which substances are present within the molecular cloud. These graphs show spectral data from three of the James Webb Space Telescope’s instruments. In addition to simple ices like water, the science team was able to identify frozen forms of a wide range of molecules, from carbon dioxide, ammonia, and methane, to the simplest complex organic molecule, methanol. In addition to the identified molecules, the team found evidence for prebiotic molecules more complex than methanol (indicated in the lower-right panel). Although they didn’t definitively attribute these signals to specific molecules, this proves for the first time that complex molecules form in the icy depths of molecular clouds before stars are born. The upper panels and lower-left panel all show the background star’s brightness versus wavelength. A lower brightness indicates absorption by ices and other materials in the molecular cloud. The lower-right panel displays the optical depth, which is essentially a logarithmic measure of how much light from the background star gets absorbed by the ices in the cloud. It is used to highlight weaker spectral features of less abundant varieties of ice. Credit: NASA, ESA, CSA, and J. Olmsted (STScI), M. K. McClure (Leiden Observatory), K. Pontoppidan (STScI), N. Crouzet (Leiden University), and Z. Smith (Open University)
The ices were detected and measured by studying how starlight from beyond the molecular cloud was absorbed by icy molecules at specific infrared wavelengths visible to Webb. This process leaves behind chemical fingerprints known as absorption spectra which can be compared with laboratory data to identify which ices are present in the molecular cloud. In this study, the team targeted ices buried in a particularly cold, dense and difficult to investigate region of the Chameleon I molecular cloud, a region 631 light-years from Earth which is currently in the process of forming dozens of young stars.
“We simply couldn’t have observed these ices without Webb,” elaborated Klaus Pontoppidan, Webb project scientist at the Space Telescope Science Institute, who was involved in this research. “The ices show up as dips against a continuum of background starlight. In regions that are this cold and dense, much of the light from the background star is blocked and Webb’s exquisite sensitivity was necessary to detect the starlight and therefore identify the ices in the molecular cloud.”
This research forms part of the Ice Age project, one of Webb’s 13 Early Release Science programs. These observations are designed to showcase Webb’s observing capabilities and allow the astronomical community to learn how to get the best from its instruments. The Ice Age team have already planned further observations, and hope to trace out the journey of ices from their formation through to the assemblage of icy comets.
“This is just the first in a series of spectral snapshots that we will obtain to see how the ices evolve from their initial synthesis to the comet-forming regions of protoplanetary discs,” concluded McClure. “This will tell us which mixture of ices — and therefore which elements — can eventually be delivered to the surfaces of terrestrial exoplanets or incorporated into the atmospheres of giant gas or ice planets.”
Webb Unveils Dark Side of Pre-stellar Ice Chemistry. This image by the NASA/ESA/CSA James Webb Space Telescope’s Near-InfraRed Camera (NIRCam) features the central region of the Chameleon I dark molecular cloud, which resides 630 light years away. The cold, wispy cloud material (blue, centre) is illuminated in the infrared by the glow of the young, outflowing protostar Ced 110 IRS 4 (orange, upper left). The light from numerous background stars, seen as orange dots behind the cloud, can be used to detect ices in the cloud, which absorb the starlight passing through them. An international team of astronomers has reported the discovery of diverse ices in the darkest, coldest regions of a molecular cloud measured to date by studying this region. This result allows astronomers to examine the simple icy molecules that will be incorporated into future exoplanets, while opening a new window on the origin of more complex molecules that are the first step in the creation of the building blocks of life. The two background stars used in this study, NIR38 and J110621 are denoted on the image in white. Credit: NASA, ESA, CSA, and M. Zamani (ESA/Webb); Science: F. Sun (Steward Observatory), Z. Smith (Open University), and the Ice Age ERS Team
Notes
[1] A molecular cloud is a vast interstellar cloud of gas and dust in which molecules can form, such as hydrogen and carbon monoxide. Cold, dense clumps in molecular clouds with higher densities than their surroundings can be the sites of star formation if these clumps collapse to form protostars.
Crushed, Zapped, Boiled, Baked And More: Nature Used 57 Recipes To Create Earth’s 10,500+ “Mineral Kinds”
Washington, DC—A 15-year study led by Carnegie’s Robert Hazen and Shaunna Morrison details the origins and diversity of every known mineral on Earth, a landmark body of work that will help reconstruct the history of life on our planet, guide the search for new minerals and ore deposits, predict possible characteristics of future life, and aid the search for habitable exoplanets and extraterrestrial life.
For more than a century, thousands of mineralogists from around the globe have carefully documented “mineral species” based on their unique combinations of chemical composition and crystal structure. Carnegie scientists Robert Hazen and Shaunna Morrison took a different approach, emphasizing how and when each kind of mineral appeared through more than 4.5 billion years of Earth history.
In twin papers published by American Mineralogist, Hazen, Morrison, and their collaborators detail how they used extensive database analysis to cluster kindred species of minerals together and distinguish new mineral species based on when and how they originated, rather than solely on their chemical and physical characteristics.
Their work indicates that the number of “mineral kinds”—a term coined in 2020 by Hazen and Morrison—totals more than 10,500. In comparison, the International Mineralogical Association recognizes about 6,000 mineral species on the basis of crystal structure and chemical composition alone.
Nature Used 57 Recipes To Create Earth’s 10,500+ “Mineral Kinds”: Pyrite forms in 21 different ways, the most of any mineral. Pyrite is so stable that it forms both at high temperature and low, both with and without water, and both with the help of microbes and in harsh environments where life plays no role whatsoever. These examples formed by the gradual precipitation of crystals from a solution rich in iron and sulfur. The large cubes are wonders of nature. Credit: ARKENSTONE/Rob Lavinsky
“This work fundamentally changes our view of the diversity of minerals on the planet,” Hazen explained. “For example, more than 80 percent of Earth’s minerals were mediated by water, which is, therefore, fundamentally important to mineral diversity on this planet. By extension, it explains one of the key reasons why the Moon and Mercury and even Mars have far fewer mineral species than Earth.”
“It also tells us something very profound about the role of biology,” he added. “One third of Earth’s minerals could not have formed without biology—shells and bones and teeth, or microbes, for example—or the vital indirect role of biology—importantly by creating an oxygen-rich atmosphere that led to 2,000 minerals that wouldn’t have formed otherwise. Each mineral specimen has a history. Each tells a story. Each is a time capsule that reveals Earth’s past as nothing else can.”
According to Hazen and Morrison—along with collaborators Sergey Krivovichev of the Russian Academy of Sciences and Robert Downs of the University of Arizona—nature created 40 percent of Earth’s mineral species by more than one method—for example, many minerals arose both abiotically and with a helping hand from living organisms—and in several cases more than 15 different “recipes” produced the same crystal structure and chemical composition.
Of the 5,659 mineral species surveyed by Hazen and colleagues, nine arose via 15 or more origin pathways, each incorporating various combinations of physical, chemical, and biological processes—everything from near-instantaneous formation by lightning or meteor strikes, to changes caused by water-rock interactions or high-pressure, high-temperature transformations that took place over hundreds of millions of years.
And, as if to demonstrate a sense of humor, nature has used 21 different ways over the last 4.56 billion years to create pyrite, also known as Fool’s Gold—the most origin stories of any mineral. Pyrite, composed of one part iron to two parts sulfide, is so stable that it forms under a huge variety of circumstances, including meteorites, volcanos, hydrothermal deposits, by pressure between layers of rock, near-surface rock weathering, in microbially-precipitated deposits, and via several mining-associated processes.
To reach their conclusions, Hazen and Morrison built a database of every known process of formation of every known mineral. Relying on large, open-access mineral databases, amplified by thousands of primary research articles on the geology of mineral localities around the world, they identified 10,556 different combinations of minerals and modes of formation.
“No one has undertaken this huge task before,” said Hazen, who honored last year by the IMA with its medal for his outstanding achievements in mineral crystal chemistry, particularly in the field of mineral evolution. “In these twin papers, we are putting forward our best effort to lay the groundwork for a new approach to recognizing different kinds of minerals. We welcome the insights, additions, and future versions of the mineralogical community.”
The papers’ groundbreaking observations and conclusions include:
Water has played a dominant role in the mineral diversity of Earth, was involved in the formation of more than 80 percent of mineral species.
Life played a direct or indirect role in the formation of almost half of known mineral species while a third of known minerals—more than 1,900 species—formed exclusively as a consequence of biological activities.
Rare elements play a disproportionate role in Earth’s mineral diversity. Just 41 elements—together constituting less than 5 parts per million of Earth’s crust—are essential constituents in some 2,400 (more than 42 percent) of Earth’s minerals. The 41 elements include arsenic, cadmium, gold, mercury, silver, titanium, tin, uranium, and tungsten.
Much of Earth’s mineral diversity was established within the planet’s first 250 million years
Some 296 known minerals are thought to pre-date Earth itself, of which 97 are known only from meteorites, with the age of some individual mineral grains estimated at 7 billion years—which was billions of years before the origin of our Solar System.
The oldest known minerals are tiny, durable zircon crystals that are almost 4.4 billion years old.
More than 600 minerals have derived from human activities, including more than 500 minerals caused by mining, 234 of them formed by coal mine fires.
Hazen, Morrison, and their colleagues propose that, complementary to the IMA-approved mineral list, new categorizations and groupings be created on the basis of a mineral’s genesis. For example, science can group 400 minerals formed by condensation at volcanic fumaroles—the openings in the Earth’s surface that emit steam and volcanic gasses.
Their papers detail other considerations in the clustering and classification of minerals, such as the eon in which they formed. For example, Earth’s so-called Great Oxidation Event about 2.3 billion years ago led new minerals to form at the planet’s near-surface. And about 4.45 billion years ago, when water first appeared, the earliest water-rock interactions may have produced as many as 350 minerals in near-surface marine and terrestrial environments.
It appears, too, that hundreds of different minerals may have formed on Earth prior to the giant impact that vaporized much of our planet’s crust and mantle and led to the Moon’s formation about 4.5 billion years ago. If so, those minerals were obliterated, only to reform as Earth cooled and solidified.
Beyond accidental mineral creations, humanity has manufactured countless thousands of mineral-like compounds that don’t qualify as minerals by the IMA standards, but do qualify as mineral kinds by Hazen and Morrison’s methodology. This includes building materials, semiconductors, laser crystals, specialty alloys, synthetic gemstones, plastic debris and the like—all “likely to persist for millions of years in the geologic record, providing a clear sedimentary horizon that marks the so-called “Anthropocene Epoch.”
Meanwhile, there are also 77 “biominerals,” that were formed by a variety of metabolic processes—this includes everything from minerals derived by corals, shells, and stinging nettles to minerals in bones, teeth, and kidney stones. Another 72 minerals originated directly or indirectly from the guano and urine of birds and bats.
The researchers noted that between the formation of oceans, the extensive development of continental crust, and perhaps even the initiation of some early form of the process that now drive plate tectonics, many important mineral-forming processes—and the origins of as many as 3,534 mineral species—took place in Earth’s first 250 million years. If so, then most of the geochemical and mineralogical environments invoked in models of life’s origins would have been present by 4.3 billion years ago.
If life is “a cosmic imperative that emerges on any mineral- and water-rich world,” the authors concluded, “then these findings support the hypothesis that life on Earth emerged rapidly, in concert with a vibrant, diverse Mineral Kingdom, in the earliest stages of planetary evolution.”
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The research was supported by the John Templeton Foundation, the NASA Astrobiology Institute ENIGMA team, and the Carnegie Institution for Science.
Bibliographic information:
On the paragenetic modes of minerals: A mineral evolution perspective, American Mineralogist (1-Jul-2022), DOI: 10.2138/am-2022-8099
Press release from Carnegie Science on the work about “mineral kinds”.
Rocks on floor of Jezero Crater, Mars, show signs of sustained interactions with water
Rocks on floor of Jezero Crater, Mars, show signs of sustained interactions with water. Perseverance rover taking a selfie over the rock it collected two core samples from on Mars. Perseverance rover taking a selfie over the rock it collected two core samples from on Mars. Image credit NASA/JPL-Caltech/MSSS
Portland, Ore., USA:Since the Perseverance rover landed in Jezero crater on Mars in February, the rover and its team of scientists back on Earth have been hard at work exploring the floor of the crater that once held an ancient lake. Perseverance and the Mars 2020 mission are looking for signs of ancient life on Mars and preparing a returnable cache of samples for later analyses on Earth.
Katie Stack Morgan is the Mars 2020 Deputy Project Scientist and a research scientist at NASA’s Jet Propulsion Laboratory (JPL), and will be providing an update on early results on the Mars 2020 rover mission on Sunday, 10 Oct., at the Geological Society of America’s Connects 2021 annual meeting in Portland, Oregon.
With Perseverance’s high-tech suite of on-board instruments, the scientific team has been analyzing the rocks of the crater floor, interpreted for now as igneous rocks, presumably a volcanic lava flow.
“The idea that this could be a volcanic rock was really appealing to us from a sample return perspective because igneous rocks are great for getting accurate age dates. Jezero was one of the few ancient crater lake sites on Mars that seemed to have both incredible sedimentary deposits as well as volcanic deposits that could help us construct the geologic time scale of Mars,” said Stack Morgan.
The lake system and rivers that drained into Jezero crater were likely active around 3.8–3.6 billion years ago, but the ability to directly date the age of the rocks in laboratories on Earth will provide the first definitive insight into the window of time that Mars may have been a habitable planet.
Using Perseverance’s abrasion tool—which scratches the top surface of the rock to reveal the rock and its textures—the team discovered that the crater floor seems to be composed of coarser-grained igneous minerals, and there are also a variety of salts in the rocks. Observations suggest that water caused extensive weathering and alteration of the crater floor, meaning that the rocks were subjected to water for a significant duration of time.
After using its on-board tools to analyze characteristics of the crater floor, the next phase was for Perseverance to collect a rock sample using its drill feature. However, after Perseverance completed its first attempt at drilling, the core sample tube came up empty.
“We spent a couple of days looking around the rover thinking that the core might have fallen out of the bit. Then we looked back down the drill hole thinking it might never have made it out of the hole. All these searches turned up empty. In the end we concluded that the core was pulverized during drilling,” said Stack Morgan.
The rock likely became so altered and weakened from interactions with water that the vibrations and strength from the Perseverance drill pulverized the sample.
Scientists then targeted another rock that appeared more resistant to weathering, and Perseverance was able to successfully collect two core samples—the first in its sample collection. Perseverance’s cache of samples will be part of a multi-spacecraft handoff, still in development, that will hopefully be returned to Earth in the early 2030s. From there, scientists in laboratories on Earth will date and analyze the rocks to see if there might be any signs of ancient Martian life.
“The rocks of the crater floor were not originally envisioned as the prime astrobiology target of the mission, but Mars always surprises us when we look up close. We are excited to find that even these rocks have experienced sustained interaction with water and could have been habitable for ancient martian microbes,” said Stack Morgan.
Astrophysicists at the University of Jena (Germany) prove that dust particles in space are mixed with ice
Clouds of interstellar dust and gas, here in the region “Cygnus-X” in the Swan constellation. Credits: ESA/PACS/SPIRE/Martin Hennemann & Frédérique Motte, Laboratoire AIM Paris-Saclay, CEA/Irfu – CNRS/INSU – Univ. Paris Diderot, France
The matter between the stars in a galaxy – called the interstellar medium – consists not only of gas, but also of a great deal of dust. At some point in time, stars and planets originated in such an environment, because the dust particles can clump together and merge into celestial bodies. Important chemical processes also take place on these particles, from which complex organic – possibly even prebiotic – molecules emerge. However, for these processes to be possible, there has to be water. In particularly cold cosmic environments, water occurs in the form of ice. Until now, however, the connection between ice and dust in these regions of space was unclear. A research team from Friedrich Schiller University Jena and the Max Planck Institute for Astronomy has now proven that the dust particles and the ice are mixed. They report their findings in the current issue of the research journal “Nature Astronomy”.
Better modelling of physico-chemical processes in space
“Until now, we didn’t know whether ice is physically separated from the dust or mixed with individual dust moieties,” explains Dr Alexey Potapov of the University of Jena. “We compared the spectra of laboratory-made silicates, water ice and their mixtures with astronomical spectra of protostellar envelopes and protoplanetary disks. We established that the spectra are congruent if silicate dust and water ice are mixed in these environments.”
Astrophysicists can gain valuable information from this data. “We need to understand different physical conditions in different astronomical environments, in order to improve the modelling of physico-chemical processes in space,” says Potapov. This result would enable researchers to better estimate the amount of material and to make more accurate statements about the temperatures in different regions of the interstellar and circumstellar media.
Water trapped in dust
Through experiments and comparisons, scientists at the University of Jena also observed what happens with water when the temperatures increase and the ice leaves the solid body to which it is bound and passes into the gas phase at about 180 Kelvin (-93 degrees Celsius).
“Some water molecules are so strongly bound to the silicate that they remain on the surface or inside dust particles,” says Potapov. “We suspect that such ‘trapped water’ also exists on or in dust particles in space. At least that is what is suggested by the comparison between the spectra obtained from the laboratory experiments and those in what is called the diffuse interstellar medium. We found clear indications that trapped water molecules exist there.”
The existence of such solid-state water suggests that complex molecules may also be present on the dust particles in the diffuse interstellar medium. If water is present on such particles, it is not a very long way to complex organic molecules, for example. This is because the dust particles usually consist of carbon, among other things, which, in combination with water and under the influence of ultraviolet radiation such as that found in the environment, promotes the formation of methanol, for example. Organic compounds have already been observed in these regions of the interstellar medium, but until now it has not been known where they originated.
The presence of solid-state water can also answer questions about another element: although we know the amount of oxygen in the interstellar medium, we previously had no information about where exactly around a third of it is located. The new research results suggest that the solid-state water in silicates is a hidden reservoir of oxygen.
Does solid-state water help in the formation of planets?
In addition, the “trapped water” can help in understanding how the dust accumulates, as it could promote the sticking together of smaller particles to form larger particles. This effect may even work in planet formation. “If we succeed in proving that ‘trapped water’ existed – or could exist – in building blocks of the Earth, there might possibly even be new answers to the question of how water came to Earth,” says Alexey Potapov. But as yet, these are only suppositions that the Jena researchers want to pursue in the future.
[1] ESA/PACS/SPIRE/Martin Hennemann & Frédérique Motte, Laboratoire AIM Paris-Saclay, CEA/Irfu – CNRS/INSU – Univ. Paris Diderot, France
INFORMATION
Original publication: A. Potapov, J. Bouwman, C. Jäger, Th. Henning (2020): Dust/ice mixing in cold regions and solid-state water in the diffuse interstellar medium, Nature astronomy, https://doi.org/10.1038/s41550-020-01214-x
Press release from the Friedrich Schiller University Jena
