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Martian Springtime Dust Storms Churn Up Surprisingly Earth-Like Cloud Patterns: Study | Sci.News

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Using images obtained by two orbiting spacecraft, NASA’s Mars Reconnaissance Orbiter and ESA’s Mars Express, planetary researchers analyzed textured dust storms that develop at the northern polar cap boundary on Mars springtime.
A spiral-shaped dust storm is visible in this image taken by the High Resolution Stereo Camera (HRSC) imager on ESA’s Mars Express spacecraft. This image, taken on May 26, 2019, depicts the formation of a spiral shape whose main arm is approximately 2,000 km in length. A granular pattern of dust cells is visible in the storm, formed by a process called closed-cell convection. This type of convection is also responsible for some cloud patterns on Earth. Image credit: ESA / DLR / FU Berlin.

A spiral-shaped dust storm is visible in this image taken by the High Resolution Stereo Camera (HRSC) imager on ESA’s Mars Express spacecraft. This image, taken on May 26, 2019, depicts the formation of a spiral shape whose main arm is approximately 2,000 km in length. A granular pattern of dust cells is visible in the storm, formed by a process called closed-cell convection. This type of convection is also responsible for some cloud patterns on Earth. Image credit: ESA / DLR / FU Berlin.

“Springtime season in Mars’ northern hemisphere is characterized by rich atmospheric dynamical activity that takes place at the edge of the polar cap, often revealed by the presence of local dust storms,” said lead author Dr. Agustín Sánchez-Levaga from the Universidad del País Vasco and colleagues.

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“Disturbances are triggered by the temperature gradient between the receding polar ice layer and the surrounding terrain, enhanced by the orographic properties of the northern hemisphere.”

“These dynamical instabilities show a variety of morphologies in images from orbit spacecraft, variously organized in cyclonic spirals, arc shapes, bands and commas, sometimes accompanied by water ice clouds.”

“We focus in a particular case of textured dust storms characterized by the presence of large areas of organized granular or cellular patterns, mixed with other forms denoted as puffy and pebbled, and ruffled elongated features.”

The researchers analyzed images from the Visual Monitoring Camera (VMC) and the High Resolution Stereo Camera (HRSC) onboard ESA’s Mars Express spacecraft and the MARCI camera on NASA’s Mars Reconnaissance Orbiter covering the period from March 3 to July 17, 2019.

This period corresponds to the early springtime season in the northern hemisphere, about one Earth year after the global dust storm of 2018.

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“The sequence of VMC images shows that the storms appear to grow and disappear in repeated cycles over a period of days, exhibiting common features and shapes,” the scientists said in a statement.

“Spiral shapes are notably visible in the wider views of the HRSC images.”

“The spirals are between 1,000 and 2,000 km in length, and their origin is the same as that of the extratropical cyclones observed in Earth’s mid-latitudes and polar latitudes.”

“The images reveal a particular phenomenon on Mars,” they added.

“They show that the Martian dust storms are made up of regularly spaced smaller cloud cells, arranged like grains or pebbles. The texture is also seen in clouds in Earth’s atmosphere.”

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Comparing the cloud patterns in dust storms on Mars with closed convection cells in Earth’s atmosphere. The image on the left depicts a storm at the Martian North Pole in May 2019, as seen from the Visual Monitoring Camera (VMC) on ESA’s Mars Express spacecraft. The repeated pattern of small cloud cells is caused by convection currents, when dusty air is heated by the Sun and rises to forms a small cell of between 20-40 km in horizontal size. The cells are surrounded by cooler air which descends, forming a boundary which creates the granular pattern. On the right, Eumetsat/ESA Meteosat-8 mission captured closed-cell convection on Earth. This image was taken on March 20, 2020, over the Azores. The cellular pattern is created in a similar process to the pattern on Mars, with similar sizes of 20-50 km. However, instead of dust, the air columns contain water vapor which is heated and rises to form clouds. Image credit: ESA / GCP / UPV / EHU Bilbao / Eumetsat.

Comparing the cloud patterns in dust storms on Mars with closed convection cells in Earth’s atmosphere. The image on the left depicts a storm at the Martian North Pole in May 2019, as seen from the Visual Monitoring Camera (VMC) on ESA’s Mars Express spacecraft. The repeated pattern of small cloud cells is caused by convection currents, when dusty air is heated by the Sun and rises to forms a small cell of between 20-40 km in horizontal size. The cells are surrounded by cooler air which descends, forming a boundary which creates the granular pattern. On the right, Eumetsat/ESA Meteosat-8 mission captured closed-cell convection on Earth. This image was taken on March 20, 2020, over the Azores. The cellular pattern is created in a similar process to the pattern on Mars, with similar sizes of 20-50 km. However, instead of dust, the air columns contain water vapor which is heated and rises to form clouds. Image credit: ESA / GCP / UPV / EHU Bilbao / Eumetsat.

On Earth, the rising air contains water which condenses to form clouds. The dust clouds imaged by Mars Express show the same process, but on Mars the rising air columns contain dust rather than water.

The Sun heats dust-laden air causing it to rise and form dusty cells. The cells are surrounded by areas of sinking air which have less dust. This gives rise to the granular pattern also seen in the image of clouds on Earth.

By tracking the movement of cells in the sequence of images, the wind speed can be measured. Wind blows over the cloud features at speeds of up to 140 km/h, causing the shape of the cells to elongate in the direction of the wind.

Despite the chaotic and dynamic atmospheres of Mars and Earth, nature creates these orderly patterns.

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“When thinking of a Mars-like atmosphere on Earth, one might easily think of a dry desert or polar region,” said Mars Express project scientist Dr. Colin Wilson.

“It is quite unexpected then, that through tracking the chaotic movement of dust storms, that parallels can be drawn with the processes that occur in Earth’s moist, hot, and decidedly very un-Mars-like tropical regions.”

One key insight made possible with the VMC images is the measurement of the altitude of dust clouds.

The length of the shadows they cast are measured and combined with knowledge of the Sun’s position to measure the height of the clouds above the Martian surface.

The results revealed that dust can reach approximately 6-11 km above the ground and the cells have typical horizontal sizes of 20-40 km.

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“Despite the unpredictable behavior of dust storms on Mars and the strong wind gusts that accompany them, we have seen that within their complexity, organized structures such as fronts and cellular convection patterns can emerge,” Dr. Sánchez-Levaga said.

“Such organized cellular convection is not unique to Earth and Mars; observations of the Venusian atmosphere by ESA’s Venus Express spacecraft arguably show similar patterns.”

“Our work on Mars dry convection is a further example of the value of comparative studies of similar phenomena occurring in planetary atmospheres in order to better understand the mechanisms underlying them under different conditions and environments.”

The findings were published in the journal Icarus.

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A. Sánchez-Lavega et al. 2022. Cellular patterns and dry convection in textured dust storms at the edge of Mars North Polar Cap. Icarus 387: 115183; doi: 10.1016/j.icarus.2022.115183



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A bizarre gamma-ray burst breaks the rules for these cosmic eruptions

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Astronomers have spotted a bright gamma-ray burst that upends previous theories of how these energetic cosmic eruptions occur.

For decades, astronomers thought that GRBs came in two flavors, long and short — that is, lasting longer than two seconds or winking out more quickly. Each type has been linked to different cosmic events. But about a year ago, two NASA space telescopes caught a short GRB in long GRB’s clothing: It lasted a long time but originated from a short GRB source.

“We had this black-and-white vision of the universe,” says astrophysicist Eleonora Troja of the Tor Vergata University of Rome. “This is the red flag that tells us, nope, it’s not. Surprise!”

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This burst, called GRB 211211A, is the first that unambiguously breaks the binary, Troja and others report December 7 in five papers in Nature and Nature Astronomy.

Prior to the discovery of this burst, astronomers mostly thought that there were just two ways to produce a GRB. The collapse of a massive star just before it explodes in a supernova could make a long gamma-ray burst, lasting more than two seconds (SN: 10/28/22). Or a pair of dense stellar corpses called neutron stars could collide, merge and form a new black hole, releasing a short gamma-ray burst of two seconds or less.

But there had been some outliers. A surprisingly short GRB in 2020 seemed to come from a massive star’s implosion (SN: 8/2/21). And some long-duration GRBs dating back to 2006 lacked a supernova after the fact, raising questions about their origins.

“We always knew there was an overlap,” says astrophysicist Chryssa Kouveliotou of George Washington University in Washington, D.C., who wrote the 1993 paper that introduced the two GRB categories, but was not involved in the new work. “There were some outliers which we did not know how to interpret.”

There’s no such mystery about GRB 211211A: The burst lasted more than 50 seconds and was clearly accompanied by a kilonova, the characteristic glow of new elements being forged after a neutron star smashup.

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This shows the glow of a kilonova that followed the oddball gamma-ray burst called GRB 211211A, in images from the Gemini North telescope and the Hubble Space Telescope.
This shows the glow of a kilonova that followed the oddball gamma-ray burst called GRB 211211A, in images from the Gemini North telescope and the Hubble Space Telescope.M. Zamani/International Gemini Observatory/NOIRLab/NSF/AURA, NASA, ESA

“Although we suspected it was possible that extended emission GRBs were mergers … this is the first confirmation,” says astrophysicist Benjamin Gompertz of the University of Birmingham in England, who describes observations of the burst in Nature Astronomy. “It has the kilonova, which is the smoking gun.”

NASA’s Swift and Fermi space telescopes detected the explosion on December 11, 2021, in a galaxy about 1.1 billion light-years away. “We thought it was a run-of-the-mill long gamma-ray burst,” says astrophysicist Wen-fai Fong of Northwestern University in Evanston, Ill.

It was relatively close by, as GRBs go. So that allowed Fong’s and Troja’s research groups to independently continue closely observing the burst in great detail using telescopes on the ground, the teams report in Nature.

As the weeks wore on and no supernova appeared, the researchers grew confused. Their observations revealed that whatever had made the GRB had also emitted much more optical and infrared light than is typical for the source of a long GRB.

After ruling out other explanations, Troja and colleagues compared the burst’s aftereffects with the first kilonova ever observed in concert with ripples in spacetime called gravitational waves (SN: 10/16/17). The match was nearly perfect. “That’s when many people got convinced we were talking about a kilonova,” she says.

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In retrospect, it feels obvious that it was a kilonova, Troja says. But in the moment, it felt as impossible as seeing a lion in the Arctic. “It looks like a lion, it roars like a lion, but it shouldn’t be here, so it cannot be,” she says. “That’s exactly what we felt.”

Now the question is, what happened? Typically, merging neutron stars collapse into a black hole almost immediately. The gamma rays come from material that is superheated as it falls into the black hole, but the material is scant, and the black hole gobbles it up within two seconds. So how did GRB 211211A keep its light going for almost a minute?

It’s possible that the neutron stars first merged into a single, larger neutron star, which briefly resisted the pressure to collapse into a black hole. That has implications for the fundamental physics that describes how difficult it is to crush neutrons into a black hole, Gompertz says.

Another possibility is that a neutron star collided with a small black hole, about five times the mass of the sun, instead of another neutron star. And the process of the black hole eating the neutron star took longer.

Or it could have been something else entirely: a neutron star merging with a white dwarf, astrophysicist Bing Zhang of the University of Nevada, Las Vegas and colleagues suggest in Nature. “We suggest a third type of progenitor, something very different from the previous two types,” he says.

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White dwarfs are the remnants of smaller stars like the sun, and are not as dense or compact as neutron stars. A collision between a white dwarf and a neutron star could still produce a kilonova if the white dwarf is very heavy.

The resulting object could be a highly magnetized neutron star called a magnetar (SN: 12/1/20). The magnetar could have continued pumping energy into gamma rays and other wavelengths of light, extending the life of the burst, Zhang says.

Whatever its origins, GRB 211211A is a big deal for physics. “It is important because we wanted to understand, what on Earth are these events?” Kouveliotou says.

Figuring out what caused it could illuminate how heavy elements in the universe form. And some previously seen long GRBs that scientists thought were from supernovas might actually be actually from mergers.

To learn more, scientists need to find more of these binary-busting GRBs, plus observations of gravitational waves at the same time. Trejo thinks they’ll be able to get that when the Laser Interferometer Gravitational-Wave Observatory, or LIGO, comes back online in 2023.

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“I hope that LIGO will produce some evidence,” Kouveliotou says. “Nature might be graceful and give us a couple of these events with gravitational wave counterparts, and maybe [help us] understand what’s going on.”



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In 2022, the James Webb Space Telescope brought us new views of the cosmos

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This year marked the end of a decades-long wait for astronomers. The James Webb Space Telescope is finally in action.

The telescope, which launched in December 2021, released its first science data in July (SN: 8/13/22, p. 30) and immediately began surpassing astronomers’ expectations.

“We’ve realized that James Webb is 10 times more sensitive than we predicted” for some kinds of observations, says astronomer Sasha Hinkley of the University of Exeter in England. His team released in September the telescope’s first direct image of an exoplanet (SN: 9/24/22, p. 6). He credits “the people who worked so hard to get this right, to launch something the size of a tennis court into space on a rocket and get this sensitive machinery to work perfectly. And I feel incredibly lucky to be the beneficiary of this.”

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The telescope, also known as JWST, was designed to see further back into the history of the cosmos than ever before (SN: 10/9/21 & 10/23/21, p. 26). It’s bigger and more sensitive than its predecessor, the Hubble Space Telescope. And because it looks in much longer wavelengths of light, JWST can observe distant and veiled objects that were previously hidden.

JWST spent its first several months collecting “early-release” science data, observations that test the different ways the telescope can see. “It is a very, very new instrument,” says Lamiya Mowla, an astronomer at the University of Toronto. “It will take some time before we can characterize all the different observation modes of all four instruments that are on board.”

That need for testing plus the excitement has led to some confusion for astronomers in these heady early days. Data from the telescope had been in such high demand that the operators hadn’t yet calibrated all the detectors before releasing data. The JWST team is providing calibration information so researchers can properly analyze the data. “We knew calibration issues were going to happen,” Mowla says.

The raw numbers that scientists have pulled out of some of the initial images may end up being revised slightly. But the pictures themselves are real and reliable, even though it takes some artistry to translate the telescope’s infrared data into colorful visible light (SN: 3/17/18, p. 4).

The stunning photos that follow are a few of the early greatest hits from the shiny new observatory.

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Deep space

James Webb Space Telescope first deep field image with the image on the left taken with the telescope's MIRI instrument and the image on the right taken from the NIRCam
NASA, ESA, CSA, STScI

JWST has captured the deepest views yet of the universe (above). Galaxy cluster SMACS 0723 (bluer galaxies) is 4.6 billion light-years from Earth. It acts as a giant cosmic lens, letting JWST zoom in on thousands of even more distant galaxies that shone 13 billion years ago (the redder, more stretched galaxies). The far-off galaxies look different in the mid-infrared light (above left) captured by the telescope’s MIRI instrument than they do in the near-infrared light (above right) captured by NIRCam. The first tracks dust; the second, starlight. Early galaxies have stars but very little dust.

Rings around Neptune

NASA, ESA, CSA, STSCI; IMAGE PROCESSING: JOSEPH DEPASQUALE/STSCI, NAOMI ROWE-GURNEY/NASA GODDARD SPACE FLIGHT CENTER

JWST was built to peer over vast cosmic distances, but it also provides new glimpses at our solar system neighbors. This pic of Neptune was the first close look at its delicate-looking rings in over 30 years (SN: 11/5/22, p. 5).

Under pressure

NASA, ESA, CSA, STScI, JPL-Caltech/NASA

The rings in this astonishing image are not an optical illusion. They’re made of dust, and a new ring is added every eight years when the two stars in the center of the image come close to each other. One of the stars is a Wolf-Rayet star, which is in the final stages of its life and puffing out dust. The cyclical dusty eruptions allowed scientists to directly measure for the first time how pressure from starlight pushes dust around (SN: 11/19/22, p. 6).

Galaxy hit-and-run

NASA James Webb Space Telescope/Flickr (CC BY 2.0)

With JWST’s unprecedented sensitivity, astronomers plan to compare the earliest galaxies with more modern galaxies to figure out how galaxies grow and evolve. This galactic smashup, whose main remnant is known as the Cartwheel galaxy, shows a step in that epic process (SN Online: 8/3/22). The large central galaxy (right in the above composite) has been pierced through the middle by a smaller one that fled the scene (not in view). The Hubble Space Telescope previously snapped a visible light image of the scene (top half). But with its infrared eyes, JWST has revealed much more structure and complexity in the galaxy’s interior (bottom half).

Exoplanet portrait

NASA, ESA, CSA, Aarynn Carter/UCSC, The ERS 1386 Team, Alyssa Pagan/STSCI

The gas giant HIP 65426b was the first exoplanet to have its portrait taken by JWST (each inset shows the planet in a different wavelength of light; the star symbol shows the location of the planet’s parent star). This image, released by astronomer Sasha Hinkley and colleagues, doesn’t look like much compared with some of the other spectacular space vistas from JWST. But it will give clues to what the planet’s atmosphere is made of and shows the telescope’s potential for doing more of this sort of work on even smaller, rocky exoplanets (SN: 9/24/22, p. 6).

Shake the dust off

NASA, ESA, CSA, STScI, Hubble Heritage Project/STScI/AURA; Image Processing: Joseph DePasquale, Anton M. Koekemoer and Alyssa Pagan/STScI

Another classic Hubble image updated by JWST is the Pillars of Creation. When Hubble viewed this star-forming region in visible light, it was shrouded by dust (above left). JWST’s infrared vision reveals sparkling newborn stars (above right).



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Planetary Scientists Find Evidence for Active Mantle Plume on Mars | Sci.News

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Elysium Planitia, a flat-smooth plain just north of the Martian equator, is underlain by an 4,000-km-diameter active mantle plume, according to new research by scientists from the Lunar and Planetary Laboratory at the University of Arizona.
An artist’s impression of an active mantle plume -- a large blob of warm and buoyant rock -- rising from deep inside Mars and pushing up Elysium Planitia, a plain within the planet’s northern lowlands. Image credit: Adrien Broquet & Audrey Lasbordes.

An artist’s impression of an active mantle plume — a large blob of warm and buoyant rock — rising from deep inside Mars and pushing up Elysium Planitia, a plain within the planet’s northern lowlands. Image credit: Adrien Broquet & Audrey Lasbordes.

Mars has typically been considered a geologically inactive world due to a lack of evidence of present-day tectonics and volcanic eruptions, especially compared to Earth.

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However, NASA’s InSight lander recently detected low but constant seismic activity, which may originate from a nearby system of recently formed fissures called Cerberus Fossae.

Cerberus Fossae was also the location of Mars’ most recent volcanic event 53,000 years ago.

“Mars was most active 3 to 4 billion years ago, and the prevailing view is that the planet is essentially dead today,” said Dr. Jeffrey Andrews-Hanna, a researcher at the Lunar and Planetary Laboratory at the University of Arizona.

“A tremendous amount of volcanic activity early in the planet’s history built the tallest volcanoes in the Solar System and blanketed most of the northern hemisphere in volcanic deposits,” added Dr. Adrien Broquet, also from the Lunar and Planetary Laboratory at the University of Arizona.

“What little activity has occurred in recent history is typically attributed to passive processes on a cooling planet.”

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In their study, Dr. Broquet and Dr. Andrews-Hanna analyzed the topography, gravity, and geology of Elysium Planitia, where both InSight and Cerberus Fossae are located.

Using geophysical models, the authors found evidence that the whole area sits over a mantle plume of hot material 95-285 K warmer than its surroundings. The center of the plume is located precisely at Cerberus Fossae.

Similarly to Earth, the presence of an active plume drives local sustained geological activity, including the marsquakes detected by InSight, and is the cause of the slow opening of the crust beneath the Cerberus Fossae.

These findings may indicate that Mars is only the third body in the inner Solar System, after the Earth and Venus, with currently active mantle plumes.

“Our study presents multiple lines of evidence that reveal the presence of a giant active mantle plume on present-day Mars,” Dr. Broquet said.

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“We have strong evidence for mantle plumes being active on Earth and Venus, but this isn’t expected on a small and supposedly cold world like Mars,” Dr. Andrews-Hanna added.

The findings were published in the journal Nature Astronomy.

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A. Broquet & J.C. Andrews-Hanna. Geophysical evidence for an active mantle plume underneath Elysium Planitia on Mars. Nat Astron, published online December 5, 2022; doi: 10.1038/s41550-022-01836-3



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