ST/ Capturing the onset of galaxy rotation in the early universe

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Paradigm

32 min readJul 6, 2022

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Space biweekly vol.55, 22d June — 6th July

TL;DR

After the Big Bang came the earliest galaxies. Due to the expansion of the universe, these galaxies are receding away from us. This causes their emissions to be redshifted (shifted towards longer wavelengths). By studying these redshifts, it is possible to characterize the ‘motion’ within the galaxies as well as their distance. In a new study, astronomers have now revealed a likely rotational motion of one such distant galaxy.
NASA’s Double Asteroid Redirection Test (DART) mission is the world’s first full-scale planetary defense test against potential asteroid impacts on Earth. Researchers now show that instead of leaving behind a relatively small crater, the impact of the DART spacecraft on its target could leave the asteroid near unrecognizable.
Astrophysicists have developed the first 3D simulation of the entire evolution of a jet — from its birth by a rotating black hole to its emission far from the collapsing star. Simulation shows that as the star collapses, its material falls on the disk that swirls around the black hole. This falling material tilts the disk, and, in turn, tilts the jet, which wobbles as it struggles to return to its original trajectory. The wobbling jet explains the longstanding mystery of why gamma ray bursts blink and shows that these bursts are even rarer than previously thought.
A team has used the Hubble Space Telescope to observe Jupiter’s moon, Europa, at ultraviolet wavelengths, filling in a ‘gap’ in the various wavelengths used to observe this icy water world. The team’s near-global UV maps show concentrations of sulfur dioxide on Europa’s trailing side.
Scientists combined data from NASA’s New Horizons mission with novel laboratory experiments and exospheric modeling to reveal the likely composition of the red cap on Pluto’s moon Charon and how it may have formed. This first-ever description of Charon’s dynamic methane atmosphere using new experimental data provides a fascinating glimpse into the origins of this moon’s red spot.
A new study describes how unique populations of craters on two of Saturn’s moons could help indicate the satellites’ age and the conditions of their formation. Using data from NASA’s Cassini mission, researchers have surveyed elliptical craters on Saturn’s moons Tethys and Dione for this study.
A formidable space tourism industry may have a greater climate effect than the aviation industry and undo repair to the protective ozone layer if left unregulated, according to a new study.
Specifications from an asteroid that made headline news in 2019 because it appeared to come out of nowhere and was traveling fast has just been published.
An innovative scientific instrument, the Compact Color Biofinder may change the game in the search for signs of extraterrestrial life.
Microbes taken from surface sediment near Lost Hammer Spring, Canada, about 900 km south of the North Pole, could provide a blueprint for the kind of life forms that may once have existed, or may still exist, on Mars.
Upcoming industry events. And more!

Space industry in numbers

The global smart space market size is projected to grow from USD 9.4 billion in 2020 to USD 15.3 billion by 2025, at a Compound Annual Growth Rate (CAGR) of 10.2% during the forecast period. The increasing venture capital funding and growing investments in smart space technology to drive market growth.

Analysts at Morgan Stanley and Goldman Sachs have predicted that economic activity in space will become a multi-trillion-dollar market in the coming decades. Morgan Stanley’s Space Team estimates that the roughly USD 350 billion global space industry could surge to over USD 1 trillion by 2040.

Source: Satellite Industry Association, Morgan Stanley Research, Thomson Reuters. *2040 estimates

Space industry news

Latest research

Possible Systematic Rotation in the Mature Stellar Population of a z = 9.1 Galaxy

by Tsuyoshi Tokuoka, Akio K. Inoue, Takuya Hashimoto, Richard S. Ellis, Nicolas Laporte, Yuma Sugahara, Hiroshi Matsuo, Yoichi Tamura, Yoshinobu Fudamoto, Kana Moriwaki, Guido Roberts-Borsani, Ikkoh Shimizu, Satoshi Yamanaka, Naoki Yoshida, Erik Zackrisson, Wei Zheng in The Astrophysical Journal Letters

As telescopes have become more advanced and powerful, astronomers have been able to detect more and more distant galaxies. These are some of the earliest galaxies to form in our universe that began to recede away from us as the universe expanded. In fact, the more the distance, the faster a galaxy appears to move away from us. Interestingly, we can estimate how fast a galaxy is moving, and in turn, when it was formed based on how “redshifted” its emission appears. This is similar to a phenomenon called “Doppler effect,” where objects moving away from an observer emit the light that appears shifted towards longer wavelengths (hence the term “redshift”) to the observer.

The Atacama Large Millimeter/submillimeter Array (ALMA) telescope located in the midst of the Atacama Desert in Chile is particularly well-suited for observing such redshifts in galaxy emissions. Recently, a team of international researchers including Professor Akio Inoue and graduate student Tsuyoshi Tokuoka from Waseda University, Japan, Dr. Takuya Hashimoto at University of Tsukuba, Japan, Professor Richard S. Ellis at University College London, and Dr. Nicolas Laporte, a research fellow at the University of Cambridge, UK, has observed redshifted emissions of a distant galaxy, MACS1149-JD1 (hereafter JD1), which has led them to some interesting conclusions.

Top left: ALMA [O iii] 88 μm emission moment-0 map contours on the HST/WFC3 F160W image of MACS1149-JD1 at z = 9.1. The contours show +3σ, 4σ, 5σ, and 6σ with σ = 9.4 mJy km s−1 beam−1. The synthesized beam ellipse is shown in the bottom left corner. The circle and inverse-triangle indicate the centers of [O iii] emission dynamical disk (Section 4) and ultraviolet (UV) emission, respectively. Top right: [O iii] line spectrum integrated over the area where the line was detected at >3σ. The gray shaded region indicates the ±1σ noise level. The solid curve is the best-fit Gaussian profile. Bottom left: [O iii] line velocity field overlaid on the line moment-0 contours. The velocity field is depicted only in the area where the Gaussian line profile fitting is favored with confidence >5σ. Bottom right: [O iii] line velocity dispersion map overlaid on the line moment-0 contours. The depicted area is the same as the velocity field.

“Beyond finding high-redshift, namely very distant, galaxies, studying their internal motion of gas and stars provides motivation for understanding the process of galaxy formation in the earliest possible universe,” explains Ellis.

Galaxy formation begins with the accumulation of gas and proceeds with the formation of stars from that gas. With time, star formation progresses from the center outward, a galactic disk develops, and the galaxy acquires a particular shape. As star formation continues, newer stars form in the rotating disk while older stars remain in the central part. By studying the age of the stellar objects and the motion of the stars and gas in the galaxy, it is possible to determine the stage of evolution the galaxy has reached.

Conducting a series of observations over a period of two months, the astronomers successfully measured small differences in the “redshift” from position to position inside the galaxy and found that JD1 satisfied the criterion for a galaxy dominated by rotation. Next, they modeled the galaxy as a rotating disk and found that it reproduced the observations very well. The calculated rotational speed was about 50 kilometers per second, which was compared to the rotational speed of the Milky Way disk of 220 kilometers per second. The team also measured the diameter of JD1 at only 3,000 light-years, much smaller than that of the Milky Way at 100,000 light-years across.

Top row: the [O iii] 88 μm line moment-0 map; middle row: the [O iii] line velocity field; bottom row: the UV continuum image. Left: the observations; middle: the models; right: the residuals. All images are shown in the source plane corrected for the gravitational lensing effect.

The significance of their result is that JD1 is by far the most distant and, therefore, earliest source yet found that has a rotating disk of gas and stars. Together with similar measurements of nearer systems in the research literature, this has allowed the team to delineate the gradual development of rotating galaxies over more than 95% of our cosmic history.

Furthermore, the mass estimated from the rotational speed of the galaxy was in line with the stellar mass previously estimated from the galaxy’s spectral signature, and came predominantly from that of “mature” stars that formed about 300 million years ago.

“This shows that the stellar population in JD1 formed at an even earlier epoch of the cosmic age,” says Hashimoto.

“The rotation speed of JD1 is much slower than those found in galaxies in later epochs and our Galaxy and it is likely that JD1 is at an initial stage of developing a rotational motion,” says Inoue. With the recently launched James Webb Space Telescope, the astronomers now plan to identify the locations of young and older stars in the galaxy to verify and update their scenario of galaxy formation.

Global-scale Reshaping and Resurfacing of Asteroids by Small-scale Impacts, with Applications to the DART and Hera Missions

by Sabina D. Raducan, Martin Jutzi in The Planetary Science Journal

NASA’s Double Asteroid Redirection Test (DART) mission is the world’s first full-scale planetary defense test against potential asteroid impacts on Earth. Researchers of the University of Bern and the National Centre of Competence in Research (NCCR) PlanetS now show that instead of leaving behind a relatively small crater, the impact of the DART spacecraft on its target could leave the asteroid near unrecognizable.

66 million years ago, a giant asteroid impact on the Earth likely caused the extinction of the dinosaurs. Currently no known asteroid poses an immediate threat. But if one day a large asteroid were to be discovered on a collision course with Earth, it might have to be deflected from its trajectory to prevent catastrophic consequences. Last November, the DART space probe of the US space agency NASA was launched as a first full-scale experiment of such a manoeuvre: Its mission is to collide with an asteroid and to deflect it from its orbit, in order to provide valuable information for the development of such a planetary defense system.

In a new study, researchers of the University of Bern and the National Centre of Competence in Research (NCCR) PlanetS have simulated this impact with a new method. Their results indicate that it may deform its target far more severely than previously thought.

Cumulative target mass that experienced a total strain larger than a certaintot, normalized by the initial target mass. We compare the results from a run in which the fast itegration scheme was not used (no transition) to the results from a run in which the fast scheme was used (transition). The data were analyzed at ≈1 hr after the impact.

“Contrary to what one might imagine when picturing an asteroid, direct evidence from space missions like the Japanese space agency’s (JAXA) Hayabusa2 probe demonstrate that asteroid can have a very loose internal structure — similar to a pile of rubble — that is held together by gravitational interactions and small cohesive forces,” says study lead-author Sabina Raducan from the Institute of Physics and the National Centre of Competence in Research PlanetS at the University of Bern.

Yet, previous simulations of the DART mission impact mostly assumed a much more solid interior of its asteroid target Dimorphos. “This could drastically change the outcome the collision of DART and Dimorphos, which is scheduled to take place in the coming September,” Raducan points out. Instead of leaving a relatively small crater on the 160 meter wide asteroid, DART’s impact at a speed of around 24'000 km/h could completely deform Dimorphos. The asteroid could also be deflected much more strongly and larger amounts of material could be ejected from the impact than the previous estimates predicted.

Schematic representation of the target shapes used in this study: (a) sphere, (b) oblate ellipsoid, and © prolate ellipsoid. The arrows indicate the location of the vertical (90°) and oblique (45°) impacts, and the crosses mark the impact points.

“One of the reasons that this scenario of a loose internal structure has so far not been thoroughly studied is that the necessary methods were not available,” study lead-author Sabina Raducan says.
“Such impact conditions cannot be recreated in laboratory experiments and the relatively long and complex process of crater formation following such an impact — a matter of hours in the case of DART — made it impossible to realistically simulate these impact processes up to now,” according to the researcher.
“With our novel modelling approach, which takes into account the propagation of the shock waves, the compaction and the subsequent flow of material, we were for the first time able to model the entire cratering process resulting from impacts on small, asteroids like Dimorphos,” Raducan reports. For this achievement, she was awarded by ESA and by the mayor of Nice at a workshop on the DART follow-up mission HERA.

Target morphology after DART-like impacts on spherical targets at vertical (90°) and oblique (45°) angles. The black arrows indicate the direction of impact.

In 2024, the European Space Agency ESA will send a space probe to Dimorphos as part of the space mission HERA. The aim is to visually investigate the aftermath of the DART probe impact. “To get the most out of the HERA mission, we need to have a good understanding of potential outcomes of the DART impact,” says study co-author Martin Jutzi from the Institute of Physics and the National Centre of Competence in Research PlanetS. “Our work on the impact simulations adds an important potential scenario that requires us to widen our expectations in this regard. This is not only relevant in the context of planetary defense, but also adds an important piece to the puzzle of our understanding of asteroids in general,” Jutzi concludes.

Black Hole to Photosphere: 3D GRMHD Simulations of Collapsars Reveal Wobbling and Hybrid Composition Jets

by Ore Gottlieb, Matthew Liska, Alexander Tchekhovskoy, Omer Bromberg, Aretaios Lalakos, Dimitrios Giannios, Philipp Mösta in The Astrophysical Journal Letters

A Northwestern University-led team of astrophysicists has developed the first-ever full 3D simulation of an entire evolution of a jet formed by a collapsing star, or a “collapsar.”

Because these jets generate gamma ray bursts (GRBs) — the most energetic and luminous events in the universe since the Big Bang — the simulations have shed light on these peculiar, intense bursts of light. Their new findings include an explanation for the longstanding question of why GRBs are mysteriously punctuated by quiet moments — blinking between powerful emissions and an eerily quiet stillness. The new simulation also shows that GRBs are even rarer than previously thought.

Top: 3D rendering of the σ0 = 15 jet in the inner 2 × 109 cm shows a significant tilt of the disk (orange) and jet (red) axis (horizontal) with respect to the rotation axis of the star at 45°. Although the jet is launched at different orientations at different times, it is deflected by the heavy outer cocoon material (blue gray) that engulfs the jet region toward the rotation axis at 45°. Bottom: 3D rendering of the logarithm of jet magnetization shows the deflection of the jet propagation and a drop in the magnetization from σ ∼ 10 to σ ∼ 1. Here, the jet head is located at r = 0.1 R⋆.

The new study marks the first full 3D simulation of the entire evolution of a jet — from its birth near the black hole to its emission after escaping from the collapsing star. The new model also is the highest-ever resolution simulation of a large-scale jet.

“These jets are the most powerful events in the universe,” said Northwestern’s Ore Gottlieb, who led the study. “Previous studies have tried to understand how they work, but those studies were limited by computational power and had to include many assumptions. We were able to model the entire evolution of the jet from the very beginning — from its birth by a black hole — without assuming anything about the jet’s structure. We followed the jet from the black hole all the way to the emission site and found processes that have been overlooked in previous studies.”

Gottlieb is a Rothschild Fellow in Northwestern’s Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA). He coauthored the paper with CIERA member Sasha Tchekhovskoy, an assistant professor of physics and astronomy at Northwestern’s Weinberg College of Arts and Sciences.

The most luminous phenomenon in the universe, GRBs emerge when the core of a massive star collapses under its own gravity to form a black hole. As gas falls into the rotating black hole, it energizes — launching a jet into the collapsing star. The jet punches the star until finally escaping from it, accelerating at speeds close to the speed of light. After breaking free from the star, the jet generates a bright GRB.

“The jet generates a GRB when it reaches about 30 times the size of the star — or a million times the size of the black hole,” Gottlieb said. “In other words, if the black hole is the size of a beach ball, the jet needs to expand over the entire size of France before it can produce a GRB.”

Due to the enormity of this scale, previous simulations have been unable to model the full evolution of the jet’s birth and subsequent journey. Using assumptions, all previous studies found that the jet propagates along one axis and never deviates from that axis. But Gottlieb’s simulation showed something very different. As the star collapses into a black hole, material from that star falls onto the disk of magnetized gas that swirls around the black hole. The falling material causes the disk to tilt, which, in turn, tilts the jet. As the jet struggles to realign with its original trajectory, it wobbles inside the collapsar. This wobbling provides a new explanation for why GRBs blink. During the quiet moments, the jet doesn’t stop — its emission beams away from Earth, so telescopes simply cannot observe it.

“Emission from GRBs is always irregular,” Gottlieb said. “We see spikes in emission and then a quiescent time that lasts for a few seconds or more. The entire duration of a GRB is about one minute, so these quiescent times are a non-negligible fraction of the total duration. Previous models were not able to explain where these quiescent times were coming from. This wobbling naturally gives an explanation to that phenomenon. We observe the jet when its pointing at us. But when the jet wobbles to point away from us, we cannot see its emission. This is part of Einstein’s theory of relativity.”

These wobbly jets also provide new insights into the rate and nature of GRBs. Although previous studies estimated that about 1% of collapsars produce GRBs, Gottlieb believes that GRBs are actually much rarer. If the jet were constrained to moving along one axis, then it would only cover a thin slice of the sky — limiting the likelihood of observing it. But the wobbly nature of the jet means that astrophysicists can observe GRBs at different orientations, increasing the likelihood of spotting them. According to Gottlieb’s calculations, GRBs are 10 times more observable than previously thought, which means that astrophysicists are missing 10 times fewer GRBs than previously thought.

“The idea is that we observe GRBs on the sky in a certain rate, and we want to learn about the true rate of GRBs in the universe,” Gottlieb explained. “The observed and true rates are different because we can only see the GRBs that are pointing at us. That means we need to assume something about the angle that these jets cover on the sky, in order to infer the true rate of GRBs. That is, what fraction of GRBs we are missing. Wobbling increases the number of detectable GRBs, so the correction from the observed to true rate is smaller. If we miss fewer GRBs, then there are fewer GRBs overall in the sky.”

If this is true, Gottlieb posits, then most of the jets either fail to be launched at all or never succeed in escaping from the collapsar to produce a GRB. Instead, they remain buried inside.

The radiative efficiency at r = 2 R⋆ for the jet with σ0 = 15. The jet’s wobbling motion is responsible for two features in the signal: (i) long quiescent times at all viewing angles and (ii) observers far from the polar axis, at θt + θj , can detect high radiative efficiency. However, we find that in general, the efficiency decreases with angular distance from the axis.

The new simulations also revealed that some of the magnetic energy in the jets partially converts to thermal energy. This suggests that the jet has a hybrid composition of magnetic and thermal energies, which produce the GRB. In a major step forward in understanding the mechanisms that power GRBs, this is the first time researchers have inferred the jet composition of GRBs at the time of emission.

“Studying jets enables us to ‘see’ what happens deep inside the star as it collapses,” Gottlieb said. “Otherwise, it’s difficult to learn what happens in a collapsed star because light cannot escape from the stellar interior. But we can learn from the jet emission — the history of the jet and the information that it carries from the systems that launch them.”

The major advance of the new simulation partially lies in its computational power. Using the code “H-AMR” on supercomputers at the Oak Ridge Leadership Computing Facility in Oak Ridge, Tennessee, the researchers developed the new simulation, which uses graphical processing units (GPUs) instead of central processing units (CPUs). Extremely efficient at manipulating computer graphics and image processing, GPUs accelerate the creation of images on a display.

Radar and Optical Characterization of Near-Earth Asteroid 2019 OK

by Luisa Fernanda Zambrano-Marin, Ellen S. Howell, Patrick A. Taylor, Sean E. Marshall, Maxime Devogèle, Anne K. Virkki, Dylan C. Hickson, Edgard G. Rivera-Valentín, Flaviane C. F. Venditti, Jon D. Giorgini in The Planetary Science Journal

When asteroid 2019 OK suddenly appeared barreling toward Earth on July 25, 2019, Luisa Fernanda Zambrano-Marin and the team at the Arecibo Observatory in Puerto Rico jumped into action.

After getting an alert, the radar scientists zoned in on the asteroid, which was coming from Earth’s blind spot — solar opposition. Zambrano-Marin and the team had 30 minutes to get as many radar readings as they could. It was traveling so fast, that’s all the time she’d have it in Arecibo’s sights. UCF manages the Arecibo Observatory for the U.S. National Science Foundation under a cooperative agreement. The asteroid made headline news because it appeared to come out of nowhere and was traveling fast. Zambrano-Marin’s findings promotes global awareness to help educate the public about these potential threats.

“It was a real challenge,” says Zambrano-Marin, a UCF planetary scientist. “No one saw it until it was practically passing by, so when we got the alert, we had very little time to act. Even so, we were able to capture a lot of valuable information.”

Range–Doppler images of each scan (1–17, left to right and top to bottom) and the sum of all 17 scans (bottom right frame) using 0.5 μs baud with a resolution of 75 m per pixel in range and 15.3 Hz in Doppler. Delay (range) increases along the vertical axis from bottom to top, and Doppler increases along the horizontal axis from left to right in each frame. The signals are spread over two to three columns (Doppler frequency) and one or two rows (delay) throughout the sequence. Total observation time 6.18 minutes with 3 s per scan.

Turns out the asteroid was between .04 and .08 miles in diameter and was moving fast. It was rotating at 3 to 5 minutes. That means it is part of only 4.2 percent of the known fast rotating asteroids. This is a growing group that the researchers say need more attention. The data indicates that the asteroid is likely a C-type, which are made up of clay and silicate rocks, or S-type, which are made up of silicate and nickel-iron. C-type asteroids are among the most common and some of the oldest in our solar system. S-type are the second most common.

Zambrano-Marin is now inspecting the data collected through Arecibo’s Planetary Radar database to continue her research. Although the observatory’s telescope collapsed in 2020, the Planetary Radar team can tap the existing data bank that spans four decades. Science operations continue in the areas of space and atmospheric sciences, and the staff is refurbishing 12-meter antennae to continue with astronomy research.

“We can use new data from other observatories and compare it to the observations we have made here over the past 40 years,” Zambrano-Marin says. “The radar data not only helps confirm information from optical observations, but it can help us identify physical and dynamical characteristics, which in turn could give us insights into appropriate deflection techniques if they were needed to protect the planet.”

Highlight of the location of 2019 OK, in terms of H magnitude versus rotation period (*Prot* ), among the general asteroid population (including Main Belt Asteroids (MBA) and NEAs) from the Light Curve Database (Warner et al. 2009) 2020 May release with quality factors greater than or equal to 2.

There are almost 30,000 known asteroids according to Center for Near Earth Studies and while few pose an immediate threat, there is a chance one of significant size could hit the earth and cause catastrophic damage. That’s why NASA keeps a close watch and system to detect and characterize objects once they are found. NASA and other space agencies nations have been launching missions to explore Near-Earth Asteroids to better understand what they are made of and how they move in anticipation of having to divert one heading for earth in the future.

The OSIRIS REx mission, which includes UCF Pegasus Professor of Physics Humberto Campins, is headed back to Earth with a sample of asteroid Bennu, which gave scientists a few surprises. Bennu was first observed at Arecibo in 1999. A new mission — NASA’s Double Asteroid Redirection Test (DART) mission — aims to demonstrate the ability to redirect an asteroid using the kinetic energy of a projectile. The spacecraft launched in November 2021 and is expected to reach its target — the Dimorphos asteroid — on September 26, 2022.

Zambrano-Marin and the rest of the team at Arecibo are working on providing the scientific community with more information about the many kinds of asteroids in the solar system to help come up with contingency plans.

Mid-ultraviolet Hubble Observations of Europa and the Global Surface Distribution of SO2

by Tracy M. Becker et al. in The Planetary Science Journal

A Southwest Research Institute-led team used the Hubble Space Telescope to observe Jupiter’s moon, Europa, at ultraviolet wavelengths, filling in a “gap” in the various wavelengths used to observe this icy water world. The team’s near-global UV maps show concentrations of sulfur dioxide on Europa’s trailing side.

SwRI will further these studies using the Europa Ultraviolet Spectrograph (Europa-UVS), which will observe Jupiter’s fourth largest moon from aboard NASA’s Europa Clipper, scheduled to launch in 2024. Scientists are almost certain that hidden beneath Europa’s icy surface is a saltwater ocean containing nearly twice as much water as is in all of Earth’s oceans. This moon may be the most promising place in our solar system suitable for some form of life beyond Earth.

Mid-UV reflectance of Europa’s leading, trailing, sub-Jovian, and anti-Jovian hemispheres. We bin the 10 centermost STIS spatial pixels and average the reflectance from the two slit positions on each hemisphere, producing one spectrum near the apex of each hemisphere. The spectra are also smoothed by 20 data points. We use the SORCE/SOLSTICE to remove the solar signal for the mid-UV assessment. The dashed line represents a linear fit to the data. The narrower bumps in the spectra, including those near 280 nm, are due to the incomplete removal of solar features. The broad 280 nm feature of interest for this work, which spans 253–305 nm, is indicated by the light purple region. The very broad 230 nm feature observed only in the leading hemisphere spectra extends from ∼200 to 260 nm.

“Europa’s relatively young surface is primarily composed of water ice, although other materials have been detected across its surface,” said Dr. Tracy Becker, lead author of a paper describing these UV observations. “Determining whether these other materials are native to Europa is important for understanding Europa’s formation and subsequent evolution.”

Assessing the surface material can provide insights into the composition of the subsurface ocean. SwRI’s dataset is the first to produce a near-global map of sulfur dioxide that correlates with large-scale darker regions in both the visible and the ultraviolet wavelengths.

“The results were not surprising, but we did get much better coverage and resolution than previous observations,” said SwRI’s Dr. Philippa Molyneux, a co-author of the paper. “Most of the sulfur dioxide is seen on the ‘trailing’ hemisphere of Europa. It’s likely concentrated there because Jupiter’s co-rotating magnetic field traps sulfur particles spewing from Io’s volcanoes and slams them against the backside of Europa.”

Io is another of Jupiter’s largest moons but, in contrast, is considered the most volcanic body in the solar system. Jupiter’s magnetic field can cause chemical reactions between the water ice and the sulfur, creating sulfur dioxide on Europa’s surface.

“In addition to studying the sulfur dioxide on the surface, we are continuing to try to understand the puzzle of why Europa — which has a surface that is known to be dominated by water ice — does not look like water ice at ultraviolet wavelengths, as confirmed by this paper,” Becker said. “We are actively working to understand why.”

Extreme Exospheric Dynamics at Charon: Implications for the Red Spot

by Ben Teolis, Ujjwal Raut, Joshua A. Kammer, Caleb J. Gimar, Carly J. A. Howett, G. Randall Gladstone, Kurt D. Retherford in Geophysical Research Letters

Southwest Research Institute scientists combined data from NASA’s New Horizons mission with novel laboratory experiments and exospheric modeling to reveal the likely composition of the red cap on Pluto’s moon Charon and how it may have formed. This first-ever description of Charon’s dynamic methane atmosphere using new experimental data provides a fascinating glimpse into the origins of this moon’s red spot as described in two recent papers.

“Prior to New Horizons, the best Hubble images of Pluto revealed only a fuzzy blob of reflected light,” said SwRI’s Randy Gladstone, a member of the New Horizons science team. “In addition to all the fascinating features discovered on Pluto’s surface, the flyby revealed an unusual feature on Charon, a surprising red cap centered on its north pole.”

Soon after the 2015 encounter, New Horizons scientists proposed that a reddish “tholin-like” material at Charon’s pole could be synthesized by ultraviolet light breaking down methane molecules. These are captured after escaping from Pluto and then frozen onto the moon’s polar regions during their long winter nights. Tholins are sticky organic residues formed by chemical reactions powered by light, in this case the Lyman-alpha ultraviolet glow scattered by interplanetary hydrogen molecules.

Left: Several key physical processes occurring at Charon considered in our exospheric modeling, including CH4 arrival onto the leading hemisphere, CH4 propagation and adsorption in the winter polar region, CH4 photo-conversion, and escape. Right: MVIC enhanced color image of Charon using MVIC’s Near IR, Red and Blue filters for RGB color (PIA19968). Charon’s red Mordor Macula terrain spreads across its north pole, shown here toward the top of the image.

“Our findings indicate that drastic seasonal surges in Charon’s thin atmosphere as well as light breaking down the condensing methane frost are key to understanding the origins of Charon’s red polar zone,” said SwRI’s Dr. Ujjwal Raut, lead author of a paper titled “Charon’s Refractory Factory” in the journal Science Advances. “This is one of the most illustrative and stark examples of surface-atmospheric interactions so far observed at a planetary body.”

The team realistically replicated Charon surface conditions at SwRI’s new Center for Laboratory Astrophysics and Space Science Experiments (CLASSE) to measure the composition and color of hydrocarbons produced on Charon’s winter hemisphere as methane freezes beneath the Lyman-alpha glow. The team fed the measurements into a new atmospheric model of Charon to show methane breaking down into residue on Charon’s north polar spot.

“Our team’s novel ‘dynamic photolysis’ experiments provided new limits on the contribution of interplanetary Lyman-alpha to the synthesis of Charon’s red material,” Raut said. “Our experiment condensed methane in an ultra-high vacuum chamber under exposure to Lyman-alpha photons to replicate with high fidelity the conditions at Charon’s poles.”

Top: Schematic showing how the “swap” of frozen methane between Charon’s polar zones causes seasonal exospheric surges near Pluto system equinoxes (dashed arrow: insolation direction change with time). Bottom: Time lapse (north polar view) of the brief exospheric maximum near autumn equinox during which the initial ∼30 μm thick methane polar cap is flash frozen (snapshots 0 and 2.5 years post equinox), followed by exospheric collapse and decades long slow accretion of the more expansive sub-micron methane frost (+42 years). Red/yellow: equatorial exospheric CH4 gas density cross section. Blue/green: Methane frost thickness. Simulation used a 10 J/m2/K/s0.5 thermal inertia and a 90° offset perihelion longitude.

SwRI scientists also developed a new computer simulation to model Charon’s thin methane atmosphere.

“The model points to ‘explosive’ seasonal pulsations in Charon’s atmosphere due to extreme shifts in conditions over Pluto’s long journey around the Sun,” said Dr. Ben Teolis, lead author of a related paper.

The team input the results from SwRI’s ultra-realistic experiments into the atmospheric model to estimate the distribution of complex hydrocarbons emerging from methane decomposition under the influence of ultraviolet light. The model has polar zones primarily generating ethane, a colorless material that does not contribute to a reddish color.

“We think ionizing radiation from the solar wind decomposes the Lyman-alpha-cooked polar frost to synthesize increasingly complex, redder materials responsible for the unique albedo on this enigmatic moon,” Raut said. “Ethane is less volatile than methane and stays frozen to Charon’s surface long after spring sunrise. Exposure to the solar wind may convert ethane into persistent reddish surface deposits contributing to Charon’s red cap.”
“The team is set to investigate the role of solar wind in the formation of the red pole,” said SwRI’s Dr. Josh Kammer, who secured continued support from NASA’s New Frontier Data Analysis Program.

A unique Saturnian impactor population from elliptical craters

by Sierra N. Ferguson, Alyssa R. Rhoden, Michelle R. Kirchoff, Julien J. Salmon in Earth and Planetary Science Letters

A new SwRI study describes how unique populations of craters on two of Saturn’s moons could help indicate the satellites’ age and the conditions of their formation. Using data from NASA’s Cassini mission, SwRI postdoctoral researcher Dr. Sierra Ferguson surveyed elliptical craters on Saturn’s moons Tethys and Dione for this study, which was co-authored by SwRI Principal Scientist Dr. Alyssa Rhoden, Lead Scientist Dr. Michelle Kirchoff and Lead Analyst Dr. Julien Salmon.

“Our work aims to answer the broader question of how old these moons are. To get at this question, my colleagues and I mapped elliptical craters on the surfaces of these moons to determine their size, direction and location on the moon,” Ferguson said.

Circular craters are very common and can be formed from a wide range of impact conditions. However, elliptical craters are rarer and form from slow and shallow impacts, which make them especially useful in determining an object’s age because shape and orientation also indicate their impactor’s trajectory.

A) Penelope, a large elliptical crater on Tethys, with its major and minor axes labeled and orientation directions noted (left) and a rose histogram showing its “orientation” (right). For each mapped crater in this study, we record the angle of the major axis, measured clockwise from 0° N, which for Penelope would be ∼1° (a north-south orientation). The image of Penelope is from the color basemaps produced by Schenk et al., 2011. B) Rose histograms of all elliptical craters mapped on Tethys (left) and Dione (right) show a strong preference for east-west oriented craters, consistent with a planetocentric source of impactors.

“By measuring the direction these craters point, we can get an idea of what the impactors that made these craters looked like in a dynamical sense and from which direction they might have hit the surface,” she said.

At first, Ferguson was not expecting to find a pattern among the directions of the elliptical craters, but she eventually noticed a trend along the equator of Dione, one of Saturn’s small moons. There, elliptical craters were overwhelmingly oriented in an east/west pattern, while the directions were more random close to the moon’s poles.

“We initially interpreted this pattern to be representative of two distinct impactor populations creating these craters,” she said. “One group was responsible for creating the elliptical craters at the equator, while another, less concentrated population may be more representative of the regular background population of impactors around Saturn.”

Ferguson also mapped elliptical craters on Tethys, Saturn’s fifth largest moon, and found that a similar size-frequency distribution of craters is unusual for objects orbiting the Sun, but curiously matches estimates for the impactor population that appears to be present on Neptune’s moon, Triton. Because that population is thought to be planetocentric, or drawn in by the ice giant’s massive gravity, Ferguson’s results point to the importance of considering planetocentric impactors when examining the age of objects in the Saturnian system. “It was really astonishing to see these patterns,” she said.

Rose histograms of elliptical crater orientations on Tethys (top) and Dione (bottom) within the geologic units described by Stephan et al. (2016) and Kirchoff and Schenk (2015), respectively.

Ferguson believes the equatorial craters could have formed from independent disks of debris orbiting each moon or potentially a single disk that affected both moons.

“Using Triton as a guide, Tethys could reasonably be billions of years old. This age estimate is dependent on how much material was available for impacting the surface and when it was available” Ferguson said. “To be certain, of course, we will need more data, but this research tells us a lot. It can give us an idea of what the formation conditions of these moons were like. Was this a system that was completely chaotic with materials hitting these satellites every which way, or was there a neat and orderly system?”

Ferguson hopes to eventually be able to compare her data from the Saturnian moons to those of Uranus, another ice giant. While current data is inconclusive, one of the flagship missions recommended by the Planetary Science Decadal Survey, which was published in April, is a mission to Uranus and its moons.

“This is the first step toward a new perspective on the cratering history of these moons and their origin and evolution,” Ferguson said.

Impact of Rocket Launch and Space Debris Air Pollutant Emissions on Stratospheric Ozone and Global Climate

by Robert G. Ryan, Eloise A. Marais, Chloe J. Balhatchet, Sebastian D. Eastham in Earth’s Future

Researchers from UCL, the University of Cambridge and Massachusetts Institute of Technology (MIT) used a 3D model to explore the impact of rocket launches and re-entry in 2019, and the impact of projected space tourism scenarios based on the recent billionaire space race.

The team found that black carbon (soot) particles emitted by rockets are almost 500 times more efficient at holding heat in the atmosphere than all other sources of soot combined (surface and aircraft) — resulting in an enhanced climate effect. Furthermore, while the study revealed that the current loss of total ozone due to rockets is small, current growth trends around space tourism indicate potential for future depletion of the upper stratospheric ozone layer in the Arctic in spring. This is because pollutants from solid-fuel rockets and re-entry heating of returning spacecraft and debris are particularly harmful to stratospheric ozone.

Study co-author Dr Eloise Marais (UCL Geography) said: “Rocket launches are routinely compared to greenhouse gas and air pollutant emissions from the aircraft industry, which we demonstrate in our work is erroneous.

Locations and fuel types of rocket launches in 2019. Marker size in the map indicates the number of launches at each location. Pie charts indicate the proportion of the four main fuel types at each launch location. Numbers above each pie chart are total propellant mass used in each country.

“Soot particles from rocket launches have a much larger climate effect than aircraft and other Earth-bound sources, so there doesn’t need to be as many rocket launches as international flights to have a similar impact. What we really need now is a discussion amongst experts on the best strategy for regulating this rapidly growing industry.”

To calculate the findings, the researchers collected information on the chemicals from all 103 rocket launches in 2019 from across the world, as well as data on reusable rocket and space junk re-entry. They also used the recent demonstrations by space tourism entrepreneurs Virgin Galactic, Blue Origin and SpaceX and proposed yearly offerings of at least daily launches by Virgin Galactic to construct a scenario of a future formidable space tourism industry. These data were then incorporated into a 3D atmospheric chemistry model to explore the impact on climate and the ozone layer.

High-latitude springtime upper stratospheric O3 loss due to rocket launch and re-entry emissions. Open circles show the O3 response to rocket emissions at 60–90° and 5 hPa altitude for years 2–10 of the decade-long 2019 rocket emissions inventory simulation. Dashed lines show the linear least squares fit to these results. Filled squares show the springtime O3 loss due to space tourism emissions at the same altitude and latitude range.

The team show that warming due to soot is 3.9 mW m-2 from a decade of contemporary rockets, dominated by emissions from kerosene-fuelled rockets. However, this more than doubles (7.9 mW m-2) after just three years of additional emissions from space tourism launches, due to the use of kerosene by SpaceX and hybrid synthetic rubber fuels by Virgin Galactic.

The researchers say this is of particular concern, as when the soot particles are directly injected into the upper atmosphere, they have a much greater effect on climate than other soot sources — with the particles 500 times more efficient at retaining heat. The team found that, under a scenario of daily or weekly space tourism rocket launches, the impact on the stratospheric ozone layer threatens to undermine the recovery experienced after the successful implementation of the Montreal Protocol. Adopted in 1987, the Montreal Protocol global ban on substances that deplete the ozone layer is considered one of the most successful international environmental policy interventions.

Study co-author Dr Robert Ryan said: “The only part of the atmosphere showing strong ozone recovery post-Montreal Protocol is the upper stratosphere, and that is exactly where the impact of rocket emissions will hit hardest. We weren’t expecting to see ozone changes of this magnitude, threatening the progress of ozone recovery.

“There is still a lot we need to find out about the influence of rocket launch and re-entry emissions on the atmosphere — in particular, the future size of the industry and the types and by-products of new fuels like liquid methane and bio-derived fuels.
“This study allows us to enter the new era of space tourism with our eyes wide open to the potential impacts. The conversation about regulating the environmental impact of the space launch industry needs to start now so we can minimise harm to the stratospheric ozone layer and climate.”

Biofinder detects biological remains in Green River fish fossils from Eocene epoch at video speed

by Anupam K. Misra, Sonia J. Rowley, Jie Zhou, Tayro E. Acosta-Maeda, Luis Dasilveira, Gregory Ravizza, Kenta Ohtaki, Tina M. Weatherby, A. Zachary Trimble, Patrick Boll, John N. Porter, Christopher P. McKay in Scientific Reports

An innovative scientific instrument, the Compact Color Biofinder, developed by a team of University of Hawai’i at Manoa researchers, may change the game in the search for signs of extraterrestrial life.

Most biological materials, for example, amino acids, fossils, sedimentary rocks, plants, microbes, proteins and lipids, have strong organic fluorescence signals that can be detected by specialized scanning cameras. In a study, the research team reported that the Biofinder is so sensitive that it can accurately detect the bio-residue in fish fossils from the 34–56 million year-old Green River formation.

“The Biofinder is the first system of its kind,” said Anupam Misra, lead instrument developer and researcher at the Hawai’i Institute of Geophysics and Planetology at the UH Manoa School of Ocean and Earth Science and Technology (SOEST). “At present, there is no other equipment that can detect minute amounts of bio-residue on a rock during the daytime. Additional strengths of the Biofinder are that it works from a distance of several meters, takes video and can quickly scan a large area.”

Biofinder detection of biological resides in fish fossil. (a) White light image of a Green River formation fish fossil, *Knightia* sp., from a distance of 50 cm using the Biofinder without laser excitation. (b) Fluorescence image of the fish fossil obtained by the Biofinder using a single laser pulse excitation, 1 µs detection time, and 3.6% gain on the CMOS detector. (c) Close-up white light image of the fish fossil cross-section using a 10× objective with 54 mm working distance showing the fish remains and rock matrix. (d) Fluorescence image with a single laser pulse excitation showing strong bio-fluorescence from the fish remains.

Though the Biofinder was first developed in 2012 by Misra, advances supported by the NASA PICASSO program culminated in the latest color version of the compact Biofinder. Finding evidence of biological residue in a vast planetary landscape is an enormous challenge. So, the team tested the Biofinder’s detection abilities on the ancient Green River fish fossils and corroborated the results through laboratory spectroscopy analysis, scanning electron microscopy and fluorescence lifetime imaging microscopy.

“There are some unknowns regarding how quickly bio-residues are replaced by minerals in the fossilization process,” said Misra. “However, our findings confirm once more that biological residues can survive millions of years, and that using biofluorescence imaging effectively detects these trace residues in real time.”

Confirmation of carbon and short-lived biofluorescence in fish fossil. (a) SEM–EDS analysis of the fish fossil cross-section showing that the fossil contains considerable quantities of carbon in comparison to the rock matrix. The rock matrix is rich in silica and has more oxygen than the fish. (b) FLIM image of the fossil cross-section showing strong bio-fluorescence in the fish (shown as false-coloured green-yellow region) with a lifetime of 2.7 ns.

The search for life — which may be existing or extinct — on planetary bodies is one of the major goals of planetary exploration missions conducted by NASA and other international space agencies.

“If the Biofinder were mounted on a rover on Mars or another planet, we would be able to rapidly scan large areas quickly to detect evidence of past life, even if the organism was small, not easy to see with our eyes, and dead for many millions of years,” said Misra. “We anticipate that fluorescence imaging will be critical in future NASA missions to detect organics and the existence of life on other planetary bodies.”
“The Biofinder’s capabilities would be critical for NASA’s Planetary Protection program, for the accurate and no-invasive detection of contaminants such as microbes or extraterrestrial biohazards to or from planet Earth,” said Sonia J. Rowley, the team biologist and co-author on the study.

Misra and colleagues are applying to have the opportunity to send the Biofinder on a future NASA mission.

“The detection of such biomarkers would constitute groundbreaking evidence for life outside of planet Earth,” said Misra.

Active lithoautotrophic and methane-oxidizing microbial community in an anoxic, sub-zero, and hypersaline High Arctic spring

by Elisse Magnuson, Ianina Altshuler, Miguel Á. Fernández-Martínez, Ya-Jou Chen, Catherine Maggiori, Jacqueline Goordial, Lyle G. Whyte in The ISME Journal

Microbes taken from surface sediment near Lost Hammer Spring, Canada, about 900 km south of the North Pole, could provide a blueprint for the kind of life forms that may once have existed, or may still exist, on Mars.

The extremely salty, very cold, and almost oxygen-free environment under the permafrost of Lost Hammer Spring in Canada’s High Arctic is the one that most closely resembles certain areas on Mars. So, if you want to learn more about the kinds of life forms that could once have existed — or may still exist — on Mars, this is a good place to look. After much searching under extremely difficult conditions, McGill University researchers have found microbes that have never been identified before. Moreover, by using state-of-the-art genomic techniques, they have gained insight into their metabolisms. In a recent paper, the scientists demonstrate, for the first time, that microbial communities found living in Canada’s High Arctic, in conditions analogous to those on Mars, can survive by eating and breathing simple inorganic compounds of a kind that have been detected on Mars (such as methane, sulfide, sulfate, carbon monoxide, and carbon dioxide). This discovery is so compelling that samples of the Lost Hammer surface sediments were selected by the European Space Agency to test the life detection capabilities of the instruments they plan to use on the next ExoMars Mission.

Lost Hammer Spring, in Nunavut in Canada’s High Arctic, is one of the coldest and saltiest terrestrial springs discovered to date. The water which travels up through 600 metres of permafrost to the surface is extremely salty (~24% salinity), perennially at sub-zero temperatures (~ — 5 °C) and contains almost no oxygen (<1ppm dissolved oxygen). The very high salt concentrations keep the Lost Hammer spring from freezing, thus maintaining a liquid water habitat even at sub-zero temperatures. These conditions are analogous to those found in certain areas on Mars, where widespread salt deposits and possible cold salt springs have been observed. And while earlier studies have found evidence of microbes in this kind of Mars-like environment — this is one of a very few studies to find microbes alive and active

To gain insight into the kind of life forms that could exist on Mars, a McGill University research team, led by Lyle Whyte of the Department of Natural Resource Sciences, has used state-of-the-art genomic tools and single cell microbiology methods to identify and characterize a novel, and more importantly, an active microbial community in this unique spring. Finding the microbes and then sequencing their DNA and mRNA was no easy task.

“It took a couple of years of working with the sediment before we were able to successfully detect active microbial communities,” explains Elisse Magnuson, a PhD student in Whyte’s lab, and the first author on the paper. “The saltiness of the environment interferes with both the extraction and the sequencing of the microbes, so when we were able to find evidence of active microbial communities, it was a very satisfying experience.”

The team isolated and sequenced DNA from the spring community, allowing them to reconstruct genomes from approximately 110 microorganisms, most of which have never been seen before. These genomes have allowed the team to determine how such creatures survive and thrive in this unique extreme environment, acted as blueprints for potential life forms in similar environments. Through mRNA sequencing, the team were able to identify active genes in the genomes and essentially identify some very unusual microbes actively metabolizing in the extreme spring environment.

“The microbes we found and described at Lost Hammer Spring are surprising, because, unlike other microorganisms, they don’t depend on organic material or oxygen to live,” adds Whyte. “Instead, they survive by eating and breathing simple inorganic compounds such as methane, sulfides, sulfate, carbon monoxide and carbon dioxide, all of which are found on Mars. They can also fix carbon dioxide and nitrogen gasses from the atmosphere, all of which makes them highly adapted to both surviving and thriving in very extreme environments on Earth and beyond.”

The next steps in the research will be to culture and further characterize the most abundant and active members of this strange microbial ecosystem, to better understand why and how they are thriving in the very cold, salty, muck of the Lost Hammer Spring. The researchers hope that this, in turn, will help in the interpretation of the exciting but enigmatic sulfur and carbon isotopes that were very recently obtained from the NASA Curiosity Rover in the Gale Crater on Mars.