Astronomy

Hubble watches spoke season on Saturn

By ScientifiCult 21 December 2023

Hubble watches spoke season on Saturn

Planet Saturn with bright white rings, multi-colored main sphere, and moons Mimas, Dione, and Enceladus. Spoke features on the left and right sides of the rings appear like faint grey smudges against the rings’ bright backdrop, about midway from the planet to the rings’ outer edge. Above the rings plane, the planet’s bands are shades of red, orange and yellow, with bright white nearer the equator. — This photo of Saturn was taken by the NASA/ESA Hubble Space Telescope on 22 October 2023, when the ringed planet was approximately 1365 million kilometres from Earth. Hubble’s ultra-sharp vision reveals a phenomenon called ring spokes.
Saturn’s spokes are transient features that rotate along with the rings. Their ghostly appearance only persists for two or three rotations around Saturn. During active periods, freshly-formed spokes continuously add to the pattern.
In 1981, NASA’s Voyager 2 first photographed the ring spokes. Hubble continues observing Saturn annually as the spokes come and go. This cycle has been captured by Hubble’s Outer Planets Atmospheres Legacy (OPAL) program that began nearly a decade ago to annually monitor weather changes on all four gas-giant outer planets.
Hubble’s crisp images show that the frequency of spoke apparitions is seasonally driven, first appearing in OPAL data in 2021 but only on the morning (left) side of the rings. Long-term monitoring shows that both the number and contrast of the spokes vary with Saturn’s seasons. Saturn is tilted on its axis like Earth and has seasons lasting approximately seven years.
This year, these ephemeral structures appear on both sides of the planet simultaneously as they spin around the giant world. Although they look small compared with Saturn, their length and width can stretch longer than Earth’s diameter!
The OPAL team notes that the leading theory is that spokes are tied to interactions between Saturn’s powerful magnetic field and the sun. Planetary scientists think that electrostatic forces generated from this interaction levitate dust or ice above the ring to form the spokes, though after several decades no theory perfectly predicts the spokes. Continued Hubble observations may eventually help solve the mystery.
Credit: Credit: NASA, ESA, STScI, A. Simon (NASA-GSFC)

This photo of Saturn was taken by the NASA/ESA Hubble Space Telescope on 22 October 2023, when the ringed planet was approximately 1365 million kilometres from Earth. Hubble’s ultra-sharp vision reveals a phenomenon called ring spokes.

Saturn’s spokes are transient features that rotate along with the rings. Their ghostly appearance only persists for two or three rotations around Saturn. During active periods, freshly-formed spokes continuously add to the pattern.

In 1981, NASA’s Voyager 2 first photographed the ring spokes. Hubble continues observing Saturn annually as the spokes come and go. This cycle has been captured by Hubble’s Outer Planets Atmospheres Legacy (OPAL) program that began nearly a decade ago to annually monitor weather changes on all four gas-giant outer planets.

Hubble’s crisp images show that the frequency of spoke apparitions is seasonally driven, first appearing in OPAL data in 2021 but only on the morning (left) side of the rings. Long-term monitoring shows that both the number and contrast of the spokes vary with Saturn’s seasons. Saturn is tilted on its axis like Earth and has seasons lasting approximately seven years.

This year, these ephemeral structures appear on both sides of the planet simultaneously as they spin around the giant world. Although they look small compared with Saturn, their length and width can stretch longer than Earth’s diameter!

The OPAL team notes that the leading theory is that spokes are tied to interactions between Saturn’s powerful magnetic field and the sun. Planetary scientists think that electrostatic forces generated from this interaction levitate dust or ice above the ring to form the spokes, though after several decades no theory perfectly predicts the spokes. Continued Hubble observations may eventually help solve the mystery. This image was created with Hubble data from proposal 16995 (A. Simon).

Press release from ESA Hubble.

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Astronomy

JWST rings in the holidays with the ringed planet Uranus

By ScientifiCult 18 December 2023

JWST rings in the holidays with the ringed planet Uranus

The NASA/ESA/CSA James Webb Space Telescope recently trained its sights on unusual and enigmatic Uranus, an ice giant that spins on its side. Webb captured this dynamic world with rings, moons, storms, and other atmospheric features — including a seasonal polar cap. The image expands upon a two-colour version released earlier this year, adding additional wavelength coverage for a more detailed look.

An image with a black background. The planet Uranus is a glowing orb near the centre surrounded by rings. The planet appears blue with a large, white patch taking up the right half. The patch is whitest at the centre, then fades into blue at it expands from right to left. A thin outline of Uranus is also white. Around the planet is a system of nested rings. There are faint orange and off-white smudges, some oval, some circular, that are background galaxies scattered throughout the image. Several bright blue point sources closer to Uranus are the planet’s moons. There is also a bright star at the left of the field, with 8 diffraction spikes. — This image of Uranus from NIRCam (Near-Infrared Camera) on the NASA/ESA/CSA James Webb Space Telescope shows the planet and its rings in new clarity. The planet’s seasonal north polar cap gleams in a bright white, and Webb’s exquisite sensitivity resolves Uranus’ dim inner and outer rings, including the Zeta ring—the extremely faint and diffuse ring closest to the planet.
This Webb image also shows 14 of the planet’s 27 moons: Oberon, Titania, Umbriel, Juliet, Perdita, Rosalind, Puck, Belinda, Desdemona, Cressida, Ariel, Miranda, Bianca, and Portia.
One day on Uranus is about 17 hours, so the planet’s rotation is relatively quick. This makes it supremely difficult for observatories with a sharp eye like Webb to capture one simple image of the entire planet – storms and other atmospheric features, and the planet’s moons, move visibly within minutes. This image combines several longer and shorter exposures of this dynamic system to correct for those slight changes throughout the observing time.
Webb’s extreme sensitivity also picks up a smattering of background galaxies—most appear as orange smudges, and there are two larger, fuzzy white galaxies to the right of the planet in this field of view.
Credit: NASA, ESA, CSA, STScI

With its exquisite sensitivity, Webb captured Uranus’ dim inner and outer rings, including the elusive Zeta ring—the extremely faint and diffuse ring closest to the planet. It also imaged many of the planet’s 27 known moons, even seeing some small moons within the rings.

In visible wavelengths, Uranus appeared as a placid, solid blue ball. In infrared wavelengths, Webb is revealing a strange and dynamic ice world filled with exciting atmospheric features.

One of the most striking of these is the planet’s seasonal north polar cap. Compared to the image from earlier this year, some details of the cap are easier to see in these newer images. These include the bright, white, inner cap and the dark lane in the bottom of the polar cap, toward the lower latitudes.

Several bright storms can also be seen near and below the southern border of the polar cap. The number of these storms, and how frequently and where they appear in Uranus’s atmosphere, might be due to a combination of seasonal and meteorological effects.

The planet Uranus on a black background. The planet appears blue with a large, white patch taking up the right half. The patch is whitest at the centre, then fades into blue as it expands from right to left. A thin outline of Uranus is also white. Around the planet is a system of nested rings. The outermost ring is the brightest while the innermost ring is the faintest. Unlike Saturn’s horizontal rings, the rings of Uranus are vertical and so they appear to surround the planet in an oval shape. There are 9 blueish white dots scattered around the rings. — This image of Uranus from NIRCam (Near-Infrared Camera) on the NASA/ESA/CSA James Webb Space Telescope shows the planet and its rings in new clarity. The Webb image exquisitely captures Uranus’s seasonal north polar cap, including the bright, white, inner cap and the dark lane in the bottom of the polar cap. Uranus’ dim inner and outer rings are also visible in this image, including the elusive Zeta ring—the extremely faint and diffuse ring closest to the planet.
This Webb image also shows 9 of the planet’s 27 moons. They are the blue dots that surround the planet’s rings. Clockwise starting at 2 o’clock, they are: Rosalind, Puck, Belinda, Desdemona, Cressida, Bianca, Portia, Juliet, and Perdita. The orbits of these moons share the 98-degree tilt of their parent planet relative to the plane of the solar system.
One day on Uranus is about 17 hours, so the planet’s rotation is relatively quick. This makes it supremely difficult for observatories with a sharp eye like Webb to capture one simple image of the entire planet – storms and other atmospheric features, and the planet’s moons, move visibly within minutes. This image combines several longer and shorter exposures of this dynamic system to correct for those slight changes throughout the observing time.
Credit: NASA, ESA, CSA, STScI

The polar cap becomes prominent when the planet’s pole begins to point towards the Sun, as it approaches solstice and receives more sunlight. Uranus reaches its next solstice in 2028, and astronomers are eager to watch any possible changes in the structure of these features. Webb will help disentangle the seasonal and meteorological effects that influence Uranus’s storms, which is critical to help astronomers understand the planet’s complex atmosphere.

Because Uranus orbits on its side at a tilt of about 98 degrees, it has the most extreme seasons in the Solar System. For nearly a quarter of each Uranian year, the Sun shines over one pole, plunging the other half of the planet into a dark, 21-year-long winter.

With Webb’s unparalleled infrared resolution and sensitivity, astronomers now see Uranus and its unique features with groundbreaking new clarity. These details, especially of the close-in Zeta ring, will be invaluable to planning any future missions to Uranus.

Uranus can also serve as a proxy for studying the many far-off, similarly sized exoplanets that have been discovered in the last few decades. This “exoplanet in our backyard” can help astronomers understand how planets of this size work, what their meteorology is like, and how they formed. This can in turn help us understand our own solar system as a whole by placing it in a larger context.

An image with a black background, a glowing orb near the centre surrounded by rings. There are smudges that are background galaxies scattered throughout the image and several bright blue point sources that are the planet’s moons. At the bottom left are compass arrows indicating the orientation of the image on the sky. Below the image is a colour key showing which filters were used to create the image and which visible-light colour is assigned to each infrared-light filter. — This image of Uranus, captured by Webb’s Near-Infrared Camera (NIRCam), shows compass arrows, scale bar, and colour key for reference.
The north and east compass arrows show the orientation of the image on the sky. Note that the relationship between north and east on the sky (as seen from below) is flipped relative to direction arrows on a map of the ground (as seen from above).
The scale bar is labelled 16 arcseconds. The length of the scale bar is approximately one-seventh the total width of the image
This image shows invisible near-infrared wavelengths of light that have been translated into visible-light colours. The colour key shows which NIRCam filters were used when collecting the light. The colour of each filter name is the visible light colour used to represent the infrared light that passes through that filter.
Webb’s NIRCam filters for this image are F140M (blue), F210M (cyan), F300M (yellow), and F460M (orange).
Credit: NASA, ESA, CSA, STScI

Press release from ESA Webb

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Astronomy

GJ 367 b, a planet with an iron heart in an extrasolar system

By ScientifiCult 15 September 2023

GJ 367 b, A PLANET WITH AN IRON HEART IN AN EXTRASOLAR SYSTEM

THE DISCOVERY MADE BY A TEAM AT THE UNIVERSITY OF TURIN ADDS TO THE PUZZLE HOW PLANETS FORM

Researchers at the University of Turin and at the Thüringer Landessternwarte have confirmed that the extrasolar planet GJ 367 b has an ultra-high density – almost twice the density of Earth. The research team also found two more planets that orbit the same star.

Over the past decades, astronomers have found several thousand extrasolar planets. Extrasolar planets orbit stars outside our solar system. The next frontier in this research field is to learn more about their composition and internal structure, in order to develop a better understanding of how planets form.

Elisa Goffo, Ph.D. student at the Physics Department of the University of Turin (Italy) and at the Thüringer Landessternwarte (Germany), together with an international research team, has made a unique discovery about the planet GJ 367 b that raises interesting questions about how planets are born. She is the lead author of the article Company for the ultra-high density, ultra-short period sub-Earth GJ 367 b: discovery of two additional low-mass planets at 11.5 and 34 days published in The Astrophysical Journal Letters.

Elisa Goffo is part of the international KESPRINT collaboration, which confirmed that the ultra-short period exoplanet GJ 367 b, whose orbital period is only 7.7 hours, is also ultra-dense. The density of a planet can be determined from its mass and radius. GJ 367 b is ultra-dense because the researchers found its density to be 10.2 grams per cubic centimeter. That is almost twice the density of Earth, suggesting that this extrasolar planet consists almost entirely of iron.

An unusual composition

Such a composition of a planet is very rare, raising questions about its formation.

“You could compare GJ 367 b to an Earth-like planet with its rocky mantle stripped away. This could have important implications for the formation of GJ 367 b. We believe that the planet might have formed like the Earth, with a dense core made mainly of iron, surrounded by a silicate-rich mantle. A catastrophic event could have stripped away its rocky mantle, leaving the dense core of the planet naked. Alternatively, GJ 367 b was born in an iron-rich region of the protoplanetary disc”,

explains Elisa Goffo. While observing GJ 367 b, the team discovered two additional low-mass planets that orbit around the star GJ 367 in 11.5 days and 34 days, respectively. These three planets and their star comprise an extrasolar system.

GJ 367 b was first found with the Transiting Exoplanet Survey Satellite (TESS), a space telescope operated by NASA. TESS uses the transit method to measure the radii of exoplanets – among other properties. In order to precisely measure the mass of GJ 367 b and confirm that the planet has a very high density, the KESPRINT researchers at the University of Turin and at the Thüringer Landessternwarte acquired nearly 300 radial velocity measurements using the HARPS spectrograph, a high-precision instrument installed at the 3.6 meter telescope operated by the European Southern Observatory (ESO) at La Silla Observatory, Chile.

“Thanks to our intensive observations with the HARPS spectrograph we discovered the presence of two additional low-mass planets with orbital periods of 11.5 and 34 days, which reduce the number of possible scenarios that might have led to the formation of such a dense planet”, says Davide Gandolfi, Professor at the University of Turin. “While GJ 367 b might have formed in an iron-rich environment, we do not exclude a formation scenario involving violent events like giant planet collisions.”

Artie Hatzes, director at the Thüringer Landessternwarte, underscores the relevance of this discovery: “GJ 367 b is an extreme case of an exoplanet. Before we can develop viable theories of its formation, we must precisely measure the planetary mass and radius. We expect an extrasolar system to consist of several planets, so it was important to search for and to find other planets orbiting in the system – to study its architecture.”

MORE INFORMATION

KESPRINT: Consisting of more than 40 members in nine countries (Czech Republic, Denmark, Germany, Italy, Japan, Spain, Sweden, UK, USA), the KESPRINT research consortium is devoted to the confirmation and characterization of transiting exoplanets found by space missions (e.g. Kepler, K2, TESS), with a special emphasis on the characterization of the smallest planets. Its members are from the Dipartimento di Fisica, Università di Torino, Italy, Thüringer Landessternwarte Tautenburg, Germany, Institute of Planetary Research, German Aerospace Center (DLR), Germany, Technische Universität Berlin, Germany, Rheinisches Institut für Umweltforschung an der Universität zu Köln, Germany, Astronomical Institute of the Czech Academy of Sciences, Czech Republic, Chalmers University of Technology, Sweden, Instituto de Astrofísica de Canarias, Spain, Mullard Space Science Laboratory, University College London, UK, University of Oxford, UK, Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus University, Denmark, Astronomy Department and Van Vleck Observatory, Wesleyan University, USA, McDonald Observatory, The University of Texas at Austin, USA, The University of Tokyo, Japan, Astrobiology Center, National Institute of Natural Sciences, Japan.

GJ 367 b and the exoplanet naming convention: Planets are usually named after their host stars, adding a lowercase letter. A planet around the star GJ 367 is called GJ 367 b, c, or d. However, the planet GJ 367 b and its star GJ 367 were named in 2022 during the “NameExoWorlds” project coordinated by the International Astronomical Union. The planet GJ 367 b is called Tahay and its star is called Añañuca, after Chilean wildflowers.

The 7.7 hours period during which GJ 367 b orbits its star stands out even among other ultra-short period planets because it is such a short orbit. One year on this planet is only 7.7 hours long. Its mass is 60 % that of Earth’s mass. Its radius is 70 % that of Earth’s radius. Therefore, it is smaller and less massive than the Earth.

Due to its proximity to the host star, the dayside surface of the planet is expected to have a temperature of almost 1.100 degrees Celsius. The star GJ 367 (Añañuca) is located roughly 31 light years from Earth, i.e., it takes about 31 years for the light to travel this distance.

How the transit method works: NASA’s TESS telescope uses the transit method to search for planets around stars other than the Sun. A transit occurs when a planet moves between its host star and us. Whenever it passes in front of its star, it blocks a small portion of the star’s light. The transit method measures this change in brightness, which yields the orbital period and inclination, the planetary radius, and other parameters.

How the radial velocity method works: The KESPRINT team observes exoplanets with the radial velocity method, which detects the existence of a planet around a star via the Doppler effect. We usually say that planets orbit stars, but that’s not entirely true: planets and stars orbit around their common center of mass! Stars emit light at different colors that become bluer or redder depending on whether the stars are moving toward or away from us while orbiting around the center of mass. When combined with the transit method, radial velocity measurements provide the mass of the planet.

The Physics Department at the University of Turin. Over the past decade, the Exoplanet group at the Physics Department of the University of Turin has focused on the detection and characterization of planets orbiting stars other than the Sun, especially those transiting their host stars, combining space-based observations with high-precision spectroscopy. The group at the University of Turin has led and coordinated the observations of GJ 367 carried out with the HARPS spectrograph.

Press release from the University of Turin.

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Astronomy

Rocks on floor of Jezero Crater, Mars, show signs of sustained interactions with water

By ScientifiCult 8 October 2021

Rocks on floor of Jezero Crater, Mars, show signs of sustained interactions with water

Jezero Crater water Mars, Perseverance rover — 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.

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GJ 1132 b: Hubble sees new atmosphere forming on the rocky exoplanet

By ScientifiCult 13 March 2021

Hubble sees new atmosphere forming on a rocky exoplanet, GJ 1132 b

The planet GJ 1132 b appears to have begun life as a gaseous world with a thick blanket of atmosphere. Starting out at several times the radius of Earth, this so-called “sub-Neptune” quickly lost its primordial hydrogen and helium atmosphere, which was stripped away by the intense radiation from its hot, young star. In a short period of time, it was reduced to a bare core about the size of Earth.

To the surprise of astronomers, new observations from Hubble [1] have uncovered a secondary atmosphere that has replaced the planet’s first atmosphere. It is rich in hydrogen, hydrogen cyanide, methane and ammonia, and also has a hydrocarbon haze. Astronomers theorise that hydrogen from the original atmosphere was absorbed into the planet’s molten magma mantle and is now being slowly released by volcanism to form a new atmosphere. This second atmosphere, which continues to leak away into space, is continually being replenished from the reservoir of hydrogen in the mantle’s magma.

“This second atmosphere comes from the surface and interior of the planet, and so it is a window onto the geology of another world,” explained team member Paul Rimmer of the University of Cambridge, UK. “A lot more work needs to be done to properly look through it, but the discovery of this window is of great importance.”

Pictured here is the region around the host star of the exoplanet GJ 1132 b. Credit:
ESA/Hubble, Digitized Sky Survey 2, CC BY 4.0.
Acknowledgement: Davide De Martin

“We first thought that these highly radiated planets would be pretty boring because we believed that they lost their atmospheres,” said team member Raissa Estrela of the Jet Propulsion Laboratory at the California Institute of Technology in Pasadena, California, USA. But we looked at existing observations of this planet with Hubble and realised that there is an atmosphere there.”

“How many terrestrial planets don’t begin as terrestrials? Some may start as sub-Neptunes, and they become terrestrials through a mechanism whereby light evaporates the primordial atmosphere. This process works early in a planet’s life, when the star is hotter,” said team leader Mark Swain of the Jet Propulsion Laboratory. “Then the star cools down and the planet’s just sitting there. So you’ve got this mechanism that can cook off the atmosphere in the first 100 million years, and then things settle down. And if you can regenerate the atmosphere, maybe you can keep it.”

In some ways, GJ 1132 b has various parallels to Earth, but in some ways it is also very different. Both have similar densities, similar sizes, and similar ages, being about 4.5 billion years old. Both started with a hydrogen-dominated atmosphere, and both were hot before they cooled down. The team’s work even suggests that GJ 1132 b and Earth have similar atmospheric pressure at the surface.

This plot shows the spectrum of the atmosphere of an Earth sized rocky exoplanet, GJ 1132 b, which is overlaid on an artist’s impression of the planet. The orange line represents the model spectrum. In comparison, the observed spectrum is shown as blue dots representing averaged data points, along with their error bars. This analysis is consistent with GJ 1132 b being predominantly a hydrogen atmosphere with a mix of methane and hydrogen cyanide. The planet also has aerosols which cause scattering of light. This is the first time a so-called “secondary atmosphere,” which was replenished after the planet lost its primordial atmosphere, has been detected on a world outside of our solar system. Credit:
NASA, ESA, and P. Jeffries (STScI)

However, the planets’ formation histories are profoundly different. Earth is not believed to be the surviving core of a sub-Neptune. And Earth orbits at a comfortable distance from our yellow dwarf Sun. GJ 1132 b is so close to its host red dwarf star that it completes an orbit the star once every day and a half. This extremely close proximity keeps GJ 1132 b tidally locked, showing the same face to its star at all times — just as our moon keeps one hemisphere permanently facing Earth.

“The question is, what is keeping the mantle hot enough to remain liquid and power volcanism?” asked Swain. “This system is special because it has the opportunity for quite a lot of tidal heating.”

The phenomenon of tidal heating occurs through friction, when energy from a planet’s orbit and rotation is dispersed as heat inside the planet. GJ 1132 b is in an elliptical orbit, and the tidal forces acting on it are strongest when it is closest to or farthest from its host star. At least one other planet in the host star’s system also exerts a gravitational pull on the planet. The consequences are that the planet is squeezed or stretched by this gravitational “pumping.” That tidal heating keeps the mantle liquid for a long time. A nearby example in our own Solar System is the Jovian moon, Io, which has continuous volcanism as a result of a tidal tug-of-war between Jupiter and the neighbouring Jovian moons.

The team believes the crust of GJ 1132 b is extremely thin, perhaps only hundreds of feet thick. That’s much too feeble to support anything resembling volcanic mountains. Its flat terrain may also be cracked like an eggshell by tidal flexing. Hydrogen and other gases could be released through such cracks.

“This atmosphere, if it’s thin — meaning if it has a surface pressure similar to Earth — probably means you can see right down to the ground at infrared wavelengths. That means that if astronomers use the James Webb Space Telescope to observe this planet, there’s a possibility that they will see not the spectrum of the atmosphere, but rather the spectrum of the surface,” explained Swain. “And if there are magma pools or volcanism going on, those areas will be hotter. That will generate more emission, and so they’ll potentially be looking at the actual geological activity — which is exciting!”

This result is significant because it gives exoplanet scientists a way to figure out something about a planet’s geology from its atmosphere,” added Rimmer. “It is also important for understanding where the rocky planets in our own Solar System — Mercury, Venus, Earth and Mars, fit into the bigger picture of comparative planetology, in terms of the availability of hydrogen versus oxygen in the atmosphere.”

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Notes:

[1] The observations were conducted as part of the Hubble observing program #14758 (PI: Zach Berta-Thomson).

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NASA’s MAVEN Observes Martian Night Sky Pulsing in Ultraviolet Light

By ScientifiCult 8 August 2020

NASA’s MAVEN Observes Martian Night Sky Pulsing in Ultraviolet Light

Vast areas of the Martian night sky pulse in ultraviolet light, according to images from NASA’s MAVEN spacecraft. The results are being used to illuminate complex circulation patterns in the Martian atmosphere.

The MAVEN team was surprised to find that the atmosphere pulsed exactly three times per night, and only during Mars’ spring and fall. The new data also revealed unexpected waves and spirals over the winter poles, while also confirming the Mars Express spacecraft results that this nightglow was brightest over the winter polar regions.

Martian night ultraviolet nightglow — This is an image of the ultraviolet “nightglow” in the Martian atmosphere. Green and white false colors represent the intensity of ultraviolet light, with white being the brightest. The nightglow was measured at about 70 kilometers (approximately 40 miles) altitude by the Imaging UltraViolet Spectrograph instrument on NASA’s MAVEN spacecraft. A simulated view of the Mars globe is added digitally for context. The image shows an intense brightening in Mars’ nightside atmosphere. The brightenings occur regularly after sunset on Martian evenings during fall and winter seasons, and fade by midnight. The brightening is caused by increased downwards winds which enhance the chemical reaction creating nitric oxide which causes the glow.
**Credits: NASA/MAVEN/Goddard Space Flight Center/CU/LASP**

“MAVEN’s images offer our first global insights into atmospheric motions in Mars’ middle atmosphere, a critical region where air currents carry gases between the lowest and highest layers,” said Nick Schneider of the University of Colorado’s Laboratory for Atmospheric and Space Physics (LASP), Boulder, Colorado. The brightenings occur where vertical winds carry gases down to regions of higher density, speeding up the chemical reactions that create nitric oxide and power the ultraviolet glow. Schneider is instrument lead for the MAVEN Imaging Ultraviolet Spectrograph (IUVS) instrument that made these observations, and lead author of a paper on this research appearing August 6 in the Journal of Geophysical Research, Space Physics. Ultraviolet light is invisible to the human eye but detectable by specialized instruments.

The diagram explains the cause of Mars’ glowing nightside atmosphere. On Mars’ dayside, molecules are torn apart by energetic solar photons. Global circulation patterns carry the atomic fragments to the nightside, where downward winds increase the reaction rate for the atoms to reform molecules. The downwards winds occur near the poles at some seasons and in the equatorial regions at others. The new molecules hold extra energy which they emit as ultraviolet light.
**Credits: NASA/MAVEN/Goddard Space Flight Center/CU/LASP**

“The ultraviolet glow comes mostly from an altitude of about 70 kilometers (approximately 40 miles), with the brightest spot about a thousand kilometers (approximately 600 miles) across, and is as bright in the ultraviolet as Earth’s northern lights,” said Zac Milby, also of LASP. “Unfortunately, the composition of Mars’ atmosphere means that these bright spots emit no light at visible wavelengths that would allow them to be seen by future Mars astronauts. Too bad: the bright patches would intensify overhead every night after sunset, and drift across the sky at 300 kilometers per hour (about 180 miles per hour).”

The pulsations reveal the importance of planet-encircling waves in the Mars atmosphere. The number of waves and their speed indicates that Mars’ middle atmosphere is influenced by the daily pattern of solar heating and disturbances from the topography of Mars’ huge volcanic mountains. These pulsating spots are the clearest evidence that the middle atmosphere waves match those known to dominate the layers above and below.

“MAVEN’s main discoveries of atmosphere loss and climate change show the importance of these vast circulation patterns that transport atmospheric gases around the globe and from the surface to the edge of space.” said Sonal Jain, also of LASP.

Next, the team plans to look at nightglow “sideways”, instead of down from above, using data taken by IUVS looking just above the edge of the planet. This new perspective will be used to understand the vertical winds and seasonal changes even more accurately.

The Martian nightglow was first observed by the SPICAM instrument on the European Space Agency’s Mars Express spacecraft. However, IUVS is a next-generation instrument better able to repeatedly map out the nightside glow, finding patterns and periodic behaviors. Many planets including Earth have nightglow, but MAVEN is the first mission to collect so many images of another planet’s nightglow.

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The research was funded by the MAVEN mission. MAVEN’s principal investigator is based at the University of Colorado’s Laboratory for Atmospheric and Space Physics, Boulder, and NASA Goddard manages the MAVEN project. NASA is exploring our Solar System and beyond, uncovering worlds, stars, and cosmic mysteries near and far with our powerful fleet of space and ground-based missions.

Press release from NASA, Goddard Space Flight Center.

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