Tag Archives: #planetaryscience

Life of a Pure Martian Design (Planetary Science)

Experimental microbially assisted chemolithotrophy provides an opportunity to trace the putative bioalteration processes of the Martian crust. A study on the Noachian Martian breccia Northwest Africa (NWA) 7034 composed of ancient (ca. 4.5 Gyr old) crustal materials from Mars, led by ERC grantee Tetyana Milojevic from the Faculty of Chemistry of the University of Vienna, now delivered a unique prototype of microbial life experimentally designed on a real Martian material. As the researchers show in the current issue of “Nature Communications Earth and Environment”, this life of a pure Martian design is a rich source of Martian-relevant biosignatures.

Early Mars is considered as an environment where life could possibly have existed. There was a time in the geological history of Mars when it could have been very similar to Earth and harbored life as we know it. In opposite to the current Mars conditions, bodies of liquid water, warmer temperature, and higher atmospheric pressure could have existed in Mars’ early history. Potential early forms of life on Mars should have been able to use accessible inventories of the red planet: derive energy from inorganic mineral sources and transform CO2 into biomass. Such living entities are rock-eating microorganisms, called “chemolithotrophs”, which are capable of transforming energy of stones to energy of life.

Martian rocks as energy source for ancient life forms

“We can assume that life forms similar to chemolithotrophs existed there in the early years of the red planet,” says astrobiologist Tetyana Milojevic, the head of Space Biochemistry group at the University of Vienna.  The traces of this ancient life (biosignatures) could have been preserved within the Noachian terrains with moisture-rich ancient geological history and mineral springs that could have been colonized by chemolithotrophs. In order to properly assess Martian relevant biosignatures, it is crucially important to consider chemolithotrophs in Martian relevant mineralogical settings.

A unique prototype of microbial life designed on a real Martian material: elemental ultrastructural analysis of an M. sedula cell grown on the genuine Noachian Martian breccia Black Beauty. (© Tetyana Milojevic)

One of rare pieces of Mars’ rocks was recently crushed to envisage how life based on Martian materials may look like. The researches used the genuine Noachian Martian breccia Northwest Africa (NWA) 7034 (nicknamed “Black Beauty”) to grow the extreme thermoacidophile Metallosphaera sedula, an ancient inhabitant of terrestrial thermal springs. This brecciated regolith sample represents the oldest known Martian crust of the ancient crystallization ages (ca. 4.5 Ga).

A specimen of “Black Beauty”

“Black Beauty is among the rarest substances on Earth, it is a unique Martian breccia formed by various pieces of Martian crust (some of them are dated at 4.42 ± 0.07 billion years) and ejected millions years ago from the Martian surface. We had to choose a pretty bold approach of crushing few grams of precious Martian rock to recreate the possible look of Mars’ earliest and simplest life form,” says Tetyana Milojevic, corresponding author of the study, about the probe that was provided by colleagues from Colorado, USA.

As a result, the researchers observed how a dark fine-grained groundmass of Black Beauty was biotransformed and used in order to build up constitutive parts of microbial cells in form of biomineral deposits. Utilizing a comprehensive toolbox of cutting edge techniques in fruitful cooperation with the Austrian Center for Electron Microscopy and Nanoanalysis in Graz, the researchers explored unique microbial interactions with the genuine Noachian Martian breccia down to nanoscale and atomic resolution. M. sedula living on Martian crustal material produced distinct mineralogical and metabolic fingerprints, which can provide an opportunity to trace the putative bioalteration processes of the Martian crust.

Analysing metabolic and mineralogical fingerprints

“Grown on Martian crustal material, the microbe formed a robust mineral capsule comprised of complexed iron, manganese and aluminum phosphates. Apart from the massive encrustation of the cell surface, we have observed intracellular formation of crystalline deposits of a very complex nature (Fe, Mn oxides, mixed Mn silicates). These are distinguishable unique features of growth on the Noachian Martian breccia, which we did not observe previously when cultivating this microbe on terrestrial mineral sources and a stony chondritic meteorite”, says Milojevic, who recently received an ERC Consolidator Grant for her research further investigating biogenicity of Martian materials.

4.42 billion years old Black Beauty specimen arrived at the Space Biochemistry Group, Vienna University (Milojevic Tetyana (left), Kölbl Denise) from Colorado, USA. A fragment of the genuine Noachian Martian breccia NWA 7034 (Black Beauty) used in the study. (© Oleksandra Kirpenko)

The observed multifaceted and complex biomineralization patterns of M. sedula grown on Black Beauty can be well stated by rich, diverse mineralogy and multimetallic nature of this ancient Martian meteorite. The unique biomineralization patterns of Black Beauty-grown cells of M. sedula emphasize the importance of experiments on genuine Martian materials for Mars-relevant astrobiological investigations. “Astrobiology research on Black Beauty and other similar ‘Flowers of the Universe’ can deliver priceless knowledge for the analysis of returned Mars samples in order to assess their potential biogenicity”, concludes Milojevic.

Featured image: A unique prototype of microbial life designed on a real Martian material: the scanning transmission electron microscopy image of M. sedula cell grown on Black Beauty. Image reveals nonhomogeneous, rugged and coarse cellular interior of M. sedula filled with crystalline deposits. (© Tetyana Milojevic)


Publication in Communications Earth & Environment:
T. Milojevic, M. Albu, D. Kölbl, G. Kothleitner, R. Bruner, M. Morgan “Chemolithotrophy on the Noachian Martian breccia NWA 7034 via experimental microbial biotransformation. Nature Communications Earth & Environment (2021), DOI: 10.1038/s43247-021-00105-x


Provided by University of Wein

Things That Game Of Thrones Can Teach Us About Science (Science)

It might be called “fantasy” for a reason, but it turns out that even some of the most magical elements of “Game of Thrones” — the super-popular book series that became a super-popular HBO series — has some roots in science. Even better, knowing how can teach us even more about how real-world science works. Here are five lessons you can learn about real science from the fantasy world of the Seven Kingdoms.

1) CHEMISTRY: WILDFIRE

Wildfire is such a terrifying weapon that it’s no wonder that, according to Game of Thrones lore, its recipe is a closely guarded secret. It’s described as a volatile green liquid that catches fire easily and burns until its fuel is exhausted. It can ignite any material and will even continue to burn while floating on water.

It turns out that there have been real-life versions of something akin to wildfire throughout history. Most mysterious is probably Greek Fire, a liquid that seventh-century Eastern Roman armies would spray on enemy ships, where it would burst into flames on contact. Though no one is sure what it was made of, rumors have included everything from sulfur and liquid petroleum to quicklime, bitumen, and burning pitch. Centuries later, the sticky, long-burning liquid weapon known as napalm hit the scene, and its horrific destruction when in the hands American forces during the Vietnam war led to its outlaw (at least for its use against civilians) in 1980.

Of course, neither of those substances are green, and both burn with a boring orange flame. But it really is possible to make a liquid that burns with a green flame that ignites whatever it touches. Last month, Youtubers Nick Uhas and Trace Dominguez made their own version of wildfire with boric acid powder, methanol, and — what else? — glowsticks. The results were pretty jaw-dropping:

We Made REAL Game of Thrones Wild Fire! | Nickipedia

2) LINGUISTICS: DOTHRAKI

While most characters in Game of Thrones speak English, a few cultures speak languages wholly invented for the series. The nomadic horse warriors known as the Dothraki speak one such language, which (along with the Valyrian language) George R.R. Martin made up for the few phrases he included in the book series. But for the TV show, the producers needed more than just a few lines of these foreign tongues — and that’s why they turned to linguist David J. Peterson.

Languages like Dothraki and Valyrian are what’s known as constructed languages or “conlangs,” and Peterson is an expert conlanger who’s constructed languages for a number of shows on television. The brilliance of a language constructed by a professional linguist is that it uses the rules of linguistics, so understanding how Peterson constructed Dothraki or Valyrian can tell you more about how your own language works. Luckily, Peterson explained just that in a 2015 op-ed for the LA Times.

3) ENGINEERING: THE WALL

Of all of the fantasies that fill Game of Thrones, The Wall might be the most outlandish (and that’s saying something). The Wall is a 700-foot (200-meter) tall, 300-mile (500-kilometer) long fortification that divides the realm of the Seven Kingdoms from the no man’s land further north. Normally, to build something this tall requires a hollow steel skeleton, deep piles (aka stakes that keep it planted to the ground), and, oh yeah, an incredibly tall crane. Although there have been cultures who achieved such a feat without modern technology — the ancient Egyptians likely combined a ramp with a rope and pulley system to pile the bricks of the pyramids — no one past or present has ever done such a thing with ice. Trace Dominguez gets into the hypothetical challenges involved with building this monstrosity in the video below.

Could We Actually Build The Wall from Game of Thrones?

4) NEUROSCIENCE: HODOR

Hodor, a “simple-minded” servant of House Stark, was actually born with a different name, but people began calling him “Hodor” because that’s the only word he can say. It’s not that he can’t communicate — he’ll utter this word with varying emphasis — it’s just that he can’t actually use other words. The show eventually explains why, but there’s a real-life explanation as well: If Hodor existed in the real world, he’d likely be suffering from Broca’s aphasia. This condition is caused by a lesion in the language-centric region of the brain known as Broca’s area, and the first patient documented with the condition could also utter only one word. His name was Louis Victor Borges, but just like Hodor, people called him by the only word he could say: “Tan.”

5) PLANETARY SCIENCE: WINTER IS COMING

Even if you’re not a Game of Thrones fan, you’ve no doubt heard the phrase “Winter is coming.” That’s uttered time and time again in the earlier seasons of the show because the story is set in a world that has long, unpredictable seasons — which means that winter could come at any time and last for years. George R.R. Martin has specifically addressed his fans’ desire to come up with a scientific explanation for the seasons: “I have to say, ‘Nice try, guys, but you’re thinking in the wrong direction.’ This is a fantasy series. I am going to explain it all eventually, but it’s going to be a fantasy explanation.”

Fantasy explanations aside, a number of scientists have weighed in on this with some pretty persuasive scientific explanations. For example, a planet’s seasons come from a tilt in its axis. The more tilted it is, the longer the seasons, which is why Uranus’s 98-degree tilt gives it 42 years of winter. It’s possible that the Game of Thrones planet has seasons of an unpredictable length because it has a “wobbly” axis that shifts its angle throughout its orbit. The strange seasons could also come down to a complicated Milankovitch cycle, the combination of quirks in orbit, axial tilt, and precession (the change in direction of the axis) that create their own change in weather and season.

The explanation could also just come down to climate science: Maybe the volcanoes of the Valyrian peninsula erupt every so often, filling the atmosphere with clouds of sulphuric acid that block out sunshine and create something akin to winter. While none of these explanations will ever come out in the show, they at least help us learn more about science in the real world.


Caplan Calculated When Universe Will Gonna End With Black Dwarf Supernova (Astronomy / Planetary Science)

Friends, new theoretical work by Caplan, an assistant professor of physics at Illinois State University, finds that many white dwarfs may explode in supernova in the distant far future, long after everything else in the universe has died and gone quiet.

In the universe now, the dramatic death of massive stars in supernova explosions comes when internal nuclear reactions produce iron in the core. Iron cannot be burnt by stars- it accumulates like a poison, triggering the star’s collapse creating a supernova. But smaller stars tend to die with a bit more dignity, shrinking and becoming white dwarfs at the end of their lives.

Stars less than about 10 times the mass of the sun do not have the gravity or density to produce iron in their cores the way massive stars do, so they can’t explode in a supernova right now. As white dwarfs cool down over the next few trillion years, they’ll grow dimmer, eventually freeze solid, and become ‘black dwarf’ stars that no longer shine. Like white dwarfs today, they’ll be made mostly of light elements like carbon and oxygen and will be the size of the earth but contain about as much mass as the sun, their insides squeezed to densities millions of times greater than anything on earth.

But just because they’re cold doesn’t mean nuclear reactions stop. Stars shine because of thermonuclear fusion—they’re hot enough to smash small nuclei together to make larger nuclei, which releases energy. White dwarfs are ash, they’re burnt out, but fusion reactions can still happen because of quantum tunneling, only much slower. Fusion happens, even at zero temperature, it just takes a really long time. Sir Caplan noted this is the key for turning black dwarfs into iron and triggering a supernova.

Caplan’s in his new work, calculated how long these nuclear reactions take to produce iron, and how much iron black dwarfs of different sizes need to explode. He calls his theoretical explosions “black dwarf supernova” and calculates that the first one will occur in about 10 to the 1100th years. Of course, not all black dwarfs will explode. “Only the most massive black dwarfs, about 1.2 to 1.4 times the mass of the sun, will blow.” Still, that means as many as 1 percent of all stars that exist today, about a billion trillion stars, can expect to die this way. As for the rest, they’ll remain black dwarfs.

Caplan calculates that the most massive black dwarfs will explode first, followed by progressively less massive stars, until there are no more left to go off after about 10^32000 years. At that point, the universe may truly be dead and silent.

Black dwarf supernova is the last interesting thing which will gonna happen in the universe.. By the time the first black dwarfs explode, the universe will already be unrecognizable.


References: M E Caplan. Black Dwarf Supernova in the Far Future. Monthly Notices of the Royal Astronomical Society, 2020; DOI: 10.1093/mnras/staa2262, Link: https://academic.oup.com/mnras/advance-article-abstract/doi/10.1093/mnras/staa2262/5884975?redirectedFrom=fulltext

Bright Areas On Ceres Come From Salty Water Below (Planetary Science / Astronomy)

NASA’s Dawn spacecraft gave scientists extraordinary close-up views of the dwarf planet Ceres, which lies in the main asteroid belt between Mars and Jupiter. By the time the mission ended in October 2018, the orbiter had dipped to less than 22 miles (35 kilometers) above the surface, revealing crisp details of the mysterious bright regions Ceres had become known for.

Scientists had figured out that the bright areas were deposits made mostly of sodium carbonate—a compound of sodium, carbon, and oxygen. They likely came from liquid that percolated up to the surface and evaporated, leaving behind a highly reflective salt crust. But what they hadn’t yet determined was where that liquid came from.

By analyzing data collected near the end of the mission, Dawn scientists have concluded that the liquid came from a deep reservoir of brine, or salt-enriched water. By studying Ceres’ gravity, scientists learned more about the dwarf planet’s internal structure and were able to determine that the brine reservoir is about 25 miles (40 kilometers) deep and hundreds of miles wide.

Ceres doesn’t benefit from internal heating generated by gravitational interactions with a large planet, as is the case for some of the icy moons of the outer solar system. But the new research, which focuses on Ceres’ 57-mile-wide (92-kilometer-wide) Occator Crater—home to the most extensive bright areas—confirms that Ceres is a water-rich world like these other icy bodies.

The findings also revealed the extent of geologic activity in Occator Crater..

Fig: Images of Occator Crater, seen in false-color, were pieced together to create this animated view. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

SOLVING THE BRIGHT MYSTERY

Long before Dawn arrived at Ceres in 2015, scientists had noticed diffuse bright regions with telescopes, but their nature was unknown. From its close orbit, Dawn captured images of two distinct, highly reflective areas within Occator Crater, which were subsequently named Cerealia Facula and Vinalia Faculae. (“Faculae” means bright areas.)

Scientists knew that micrometeorites frequently pelt the surface of Ceres, roughing it up and leaving debris. Over time, that sort of action should darken these bright areas. So their brightness indicates that they likely are young. Trying to understand the source of the areas, and how the material could be so new, was a main focus of Dawn’s final extended mission, from 2017 to 2018.

The research not only confirmed that the bright regions are young—some less than 2 million years old; it also found that the geologic activity driving these deposits could be ongoing. This conclusion depended on scientists making a key discovery: salt compounds (sodium chloride chemically bound with water and ammonium chloride) concentrated in Cerealia Facula.

On Ceres’ surface, salts bearing water quickly dehydrate, within hundreds of years. But Dawn’s measurements show they still have water, so the fluids must have reached the surface very recently. This is evidence both for the presence of liquid below the region of Occator Crater and ongoing transfer of material from the deep interior to the surface.

Fig: This mosaic of Ceres’ Occator Crater is composed of images NASA’s Dawn mission captured on its second extended mission, in 2018. Bright pits and mounds (foreground) were formed by salty liquid released as Occator’s water-rich floor froze after the crater-forming impact about 20 million years ago. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/USRA/LPI

Active Geology: Recent and Unusual

In our solar system, icy geologic activity happens mainly on icy moons, where it is driven by their gravitational interactions with their planets. But that’s not the case with the movement of brines to the surface of Ceres, suggesting that other large ice-rich bodies that are not moons could also be active.

Some evidence of recent liquids in Occator Crater comes from the bright deposits, but other clues come from an assortment of interesting conical hills reminiscent of Earth’s pingos—small ice mountains in polar regions formed by frozen pressurized groundwater. Such features have been spotted on Mars, but the discovery of them on Ceres marks the first time they’ve been observed on a dwarf planet.

On a larger scale, scientists were able to map the density of Ceres’ crust structure as a function of depth—a first for an ice-rich planetary body. Using gravity measurements, they found Ceres’ crustal density increases significantly with depth, way beyond the simple effect of pressure. Researchers inferred that at the same time Ceres’ reservoir is freezing, salt and mud are incorporating into the lower part of the crust.

Dawn is the only spacecraft ever to orbit two extraterrestrial destinations—Ceres and the giant asteroid Vesta—thanks to its efficient ion propulsion system. When Dawn used the last of a key fuel, hydrazine, for a system that controls its orientation, it was neither able to point to Earth for communications nor to point its solar arrays at the Sun to produce electrical power. Because Ceres was found to have organic materials on its surface and liquid below the surface, planetary protection rules required Dawn to be placed in a long-duration orbit that will prevent it from impacting the dwarf planet for decades.


References: (1) “Recent Cryovolcanic Activity at Occator Crater on Ceres,” A. Nathues et al. 2020 August 10, Nature Astronomy http://www.nature.com/articles/s41550-020-1146-8 . (2) “Impact-driven Mobilization of Deep Crustal Brines on Dwarf Planet Ceres,” C. A. Raymond et al. 2020 August 10, Nature Astronomy http://www.nature.com/articles/s41550-020-1168-2 (3) “Evidence of Non-uniform Crust of Ceres from Dawn’s High-resolution Gravity Data,” R. S. Park et al., 2020 August 10, Nature Astronomy http://www.nature.com/articles/s41550-020-1019-1 (4) “Fresh Emplacement of Hydrated Sodium Chloride on Ceres from Ascending Salty Fluids,” M. C. De Sanctis et al., 2020 August 10, Nature Astronomy http://www.nature.com/articles/s41550-020-1138-8 (5) “Impact Heat Driven Volatile Redistribution at Occator Crater on Ceres as a Comparative Planetary Process,” P. Schenk et al., 2020 August 10, Nature Communications http://www.nature.com/articles/s41467-020-17184-7 (6) “The Varied Sources of Faculae-forming Brines in Ceres’ Occator crater Emplaced via Hydrothermal Brine Effusion,” J. E. C. Scully et al., 2020 August 10, Nature Communications http://www.nature.com/articles/s41467-020-15973-8 (7) “Post-impact Cryo-hydrologic Formation of Small Mounds and Hills in Ceres’s Occator Crater,” B. E. Schmidt et al., 2020 August 10, Nature Geoscience http://www.nature.com/articles/s41561-020-0581-6

Scientists Found Atmosphere Of Mars Pulses In Ultraviolet (Astronomy)

Using new data from the Imaging Ultraviolet Spectrograph (IUVS) on NASA’s MAVEN (Mars Atmosphere and Volatile Evolution) spacecraft, scientists have found that the atmosphere of Mars pulses in ultraviolet three times per night, and only during Martian spring and fall. The IUVS data have also revealed unexpected waves and spirals over the winter poles, while also confirming previous results from ESA’s Mars Express spacecraft that this nightglow was brightest over the winter polar regions. 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.

Fig: This image shows 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 km 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. Image credit: NASA / MAVEN / NASA’s Goddard Space Flight Center / CU / LASP.

MAVEN wasn’t the first spacecraft to spot the nightglow on Mars. That honor belongs to ESA’s Mars Express mission, which entered orbit around the Red Planet in 2003.

But MAVEN was the first to capture the nightglow for what it is — a dynamic and constantly evolving phenomenon.

In the study, Dr. Schneider and colleagues used MAVEN’s IUVS instrument to snap images of Mars from a distance of 5,955 km (3,700 miles).

Those far-flung recordings allowed the team to trace the path of nightglow as it moved across the entire planet.

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.

Fig: 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. Image credit: NASA / MAVEN / NASA’s Goddard Space Flight Center / CU / LASP.

The pulsations observed by the team reveal the importance of planet-encircling waves in the Mars atmosphere.

The number of waves and their speed indicates that the Martian middle atmosphere is influenced by the daily pattern of solar heating and disturbances from the topography of the planet’s 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.

Next, the authors plan 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.


References: N.M. Schneider, N. M. Schneider Z. Milby S. K. Jain F. González‐Galindo E. Royer J.‐C. Gérard A. Stiepen J. Deighan A. I. F. Stewart F. Forget F. Lefèvre S. W. Bougher, “Imaging of Martian Circulation Patterns and Atmospheric Tides Through MAVEN/IUVS Nightglow Observations”, Journal of Geophysical Research: Space Physics, 2020; doi: 10.1029/2019JA027318 link: https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/2019JA027318

Jupiter’s Violent Storms May Form Ammonia-Water Hailstones (Astronomy / Planetary Science)

A new study suggests that during Jupiter’s violent storms, hailstones form from a cooled mixture of water and ammonia gas, similar to the process in Earth’s storms where hail forms in the presence of supercooled liquid water; growth of these Jovian hailstones, dubbed ‘mushballs,’ creates a slush-like substance surrounded by a layer of ice, and mushballs fall, evaporate, and continue sinking further in the gas giant’s deep atmosphere.

Fig: This image captured by NASA’s Juno orbiter shows a multitude of magnificent, swirling clouds in Jupiter’s North North Temperate Belt. The image was taken at 4:58 p.m. EDT on October 29, 2018 (1:58 p.m. PDT) as the spacecraft performed its 16th close flyby of Jupiter. At the time, Juno was about 4,400 miles (7,000 km) from the planet’s cloud tops, at a latitude of approximately 40 degrees north. Image credit: NASA / JPL-Caltech / SwRI / MSSS / Gerald Eichstaedt / Sean Doran.

NASA’s Juno mission revealed that Jupiter’s atmosphere is much more complex and intriguing than previously anticipated.

Most of the planet’s atmosphere was shown to be depleted — which is to say, missing — in ammonia.

While ammonia was expected to be well mixed, large scale variability of ammonia was detected at least 100 km (62 miles) below the cloud level where condensation occurs.

Dr. Scott Bolton, Juno’s principal investigator at the Southwest Research Institute, Dr. Tristan Guillot, a Juno co-investigator from the Université Côte d’Azur, and their colleagues propose a new mechanism to explain this depletion and variability.

Jupiter’s mushballs get so big, even the updrafts can’t hold them, and they fall deeper into the atmosphere, encountering even warmer temperatures, where they eventually evaporate completely. Their action drags ammonia and water down to deep levels in the planet’s atmosphere.

Fig: This graphic depicts the evolutionary process of ‘shallow lightning’ and ammonia-water mushballs. An anvil-shaped thunderstorm cloud originates about 65 km (40 miles) below Jupiter’s visible cloud deck. Powered by water-based moist convection, the cloud generates strong updrafts that move liquid water and water ice particles upward. About 19 km (12 miles) up, temperatures are so low that all of the water particles turn to ice. Still climbing, the ice particles cross a region located about 23 km (14 miles) below the upper clouds, where temperatures are between minus 85 degrees Celsius (minus 121 degrees Fahrenheit) and minus 100 degrees Celsius (minus 150 degrees Fahrenheit), depicted as green-hashed layer. At that point, ammonia vapor in the atmosphere acts like an antifreeze, melting the water-ice crystals, transforming them into ammonia-water liquid droplets which then grow and gather a solid icy shell to become mushballs. Once big enough, these slushy hailstones fall down, transporting both ammonia and water into Jupiter’s deep atmosphere where the mushballs eventually evaporate. Image credit: NASA / JPL-Caltech / SwRI / CNRS.

That explains why we don’t see much of it in these places with Juno’s Microwave Radiometer.


References: Tristan Guillot David J. Stevenson Sushil K. Atreya Scott J. Bolton Heidi N. Becker, “Storms and the Depletion of Ammonia in Jupiter: I. Microphysics of “Mushballs””, Journal of Geophysical Research: Planets, Volume 125, Issue 8, 2020, doi: https://doi.org/10.1029/2020JE006403

Solar System’s Heliosphere May Be Smaller and Rounder than Previously Thought (Astronomy / Planetary Science)

The heliosphere is a giant magnetic bubble that contains our Solar System, the solar wind and the solar magnetic field. Outside the heliosphere is the interstellar medium — the ionized gas and magnetic field that fills the space between stellar systems in our Milky Way Galaxy. The shape of the heliosphere has been explored in the past six decades. There was a consensus that its shape is comet-like. New research led by Boston University and Harvard University provides an alternative shape that lacks this long tail: the deflated croissant.

Fig: New model suggests the shape of the Sun’s bubble of influence, the heliosphere (seen in yellow), may be a deflated croissant shape, rather than the long-tailed comet shape suggested by other research. Image credit: Opher et al, doi: 10.1038/s41550-020-1036-0.

The shape of the heliosphere is difficult to measure from within. The closest edge of the heliosphere is more than 16 billion km (10 billion miles) from Earth.

Only NASA’s twin Voyager spacecraft directly measured this region, leaving us with just two points of ground-truth data on the shape of the heliosphere.

From near Earth, scientists study our boundary to interstellar space by capturing and observing particles flying toward Earth.

This includes charged particles that come from distant parts of the Galaxy, called galactic cosmic rays, along with those that were already in our Solar System, travel out towards the heliopause, and are bounced back towards Earth through a complex series of electromagnetic processes.

These are called energetic neutral atoms, and because they are created by interacting with the interstellar medium, they act as a useful proxy for mapping the edge of the heliosphere.

This is how NASA’s Interstellar Boundary Explorer (IBEX) studies the heliosphere, making use of these particles as a kind of radar, tracing out our Solar System’s boundary to interstellar space.

To make sense of these data, scientists use computer models to turn the data into a prediction of the heliosphere’s characteristics.

In the new research, Boston University’s Professor Merav Opher and colleagues used data from several NASA missions to characterize the behavior of material in space that fills the bubble of the heliosphere and get another perspective on its borders.

NASA’s Cassini mission carried an instrument — designed to study particles trapped in Saturn’s magnetic field — that also made observations of particles bouncing back towards the inner Solar System. These measurements are similar to IBEX’s, but provide a distinct perspective on the heliosphere’s boundary.

Additionally, NASA’s New Horizons mission has provided measurements of pick-up ions, particles that are ionized out in space and are picked up and move along with the solar wind.

Because of their distinct origins from the solar wind particles streaming out from the Sun, pick-up ions are much hotter than other solar wind particles — and it’s this fact that the new work hinges on.

Considering the solar wind’s components separately, combined with an earlier work by the team using the solar magnetic field as a dominant force in shaping the heliosphere, created a deflated croissant shape, with two jets curling away from the central bulbous part of the heliosphere, and notably lacking the long tail predicted by many scientists.


References: Opher, M., Loeb, A., Drake, J. et al. A small and round heliosphere suggested by magnetohydrodynamic modelling of pick-up ions. Nat Astron 4, 675–683 (2020). https://doi.org/10.1038/s41550-020-1036-0

NASA’s Curiosity Rover Marks Eight Years of Mars Exploration (Planetary Science / Astronomy)

NASA’s Curiosity rover has seen a lot since August 5, 2012, when it first set its wheels inside the huge basin of Gale Crater.

Fig: Curiosity rover took this selfie on October 11, 2019. The rover drilled twice in this location, nicknamed Glen Etive. Just left of the rover are the two drill holes, called Glen Etive 1 (right) and Glen Etive 2 (left). Image credit: NASA / JPL-Caltech / MSSS.

Curiosity, the fourth rover the United States has sent to Mars, launched November 26, 2011 and landed on the Red Planet at 10:32 p.m. PDT on August 5, 2012 (1:32 a.m. EDT on August 6, 2012).

The mission is led by NASA’s Jet Propulsion Laboratory, and involves almost 500 scientists from the United States and other countries around the world.

Curiosity explores the 154-km- (96-mile) wide Gale Crater and acquires rock, soil, and air samples for onboard analysis.

The car-size rover is about as tall as a basketball player and uses a 2.1-m- (7-foot) long arm to place tools close to rocks selected for study.

Its large size allows it to carry an advanced kit of science instruments, including 17 cameras, a laser to vaporize and study small pinpoint spots of rocks at a distance, and a drill to collect powdered rock samples:

Fig: These 26 holes represent each of the rock samples NASA’s Curiosity Mars rover has collected as of early July 2020. A map in the upper left shows where the holes were drilled along the rover’s route, along with where it scooped six samples of soil. The drill holes were taken by the MAHLI camera on the end of the rover’s robotic arm. Image credit: NASA / JPL-Caltech / MSSS.

(i) the Mars Hand Lens Imager (MAHLI) is the rover’s version of the magnifying hand lens that geologists usually carry with them into the field; MAHLI’s close-up images reveal the minerals and textures in rock surfaces;

(ii) the Mars Descent Imager (MARDI) shot a color video of the terrain below as the rover descended to its landing site; the video helped mission planners select the best path for Curiosity when the rover started exploring Gale Crater;

(iii) when the Alpha Particle X-Ray Spectrometer (APXS) is placed right next to a rock or soil surface, it uses two kinds of radiation to measure the amounts and types of chemical elements that are present.

(iv) the Chemistry and Camera (ChemCam) instrument’s laser, camera and spectrograph work together to identify the chemical and mineral composition of rocks and soils;

(v) the Chemical and Mineralogy (CheMin) performs chemical analysis of powdered rock samples to identify the types and amounts of different minerals that are present;

(vi) the Sample Analysis at Mars (SAM) is made up of three different instruments that search for and measure organic chemicals and light elements that are important ingredients potentially associated with life;

(vii) the Radiation Assessment Detector (RAD) is helping prepare for future human exploration of Mars; the instrument measures the type and amount of harmful radiation that reaches the Martian surface from the Sun and space sources;

(viii) the Dynamic Albedo of Neutrons (DAN) looks for telltale changes in the way neutrons released from Martian soil that indicate liquid or frozen water exists underground;

(ix) the Rover Environmental Monitoring Station (REMS) contains all the weather instruments needed to provide daily and seasonal reports on meteorological conditions around the rover;

(x) the Mars Science Laboratory Entry Descent and Landing Instrument (MEDLI) measured the heating and atmospheric pressure changes that occurred during the descent to help determine the effects on different parts of the spacecraft.

Since touchdown, Curiosity journeyed more than 23 km (14 miles), drilling 26 rock samples and scooping six soil samples.


References: (1) https://mars.nasa.gov/msl/mission/overview/ (2) https://mars.nasa.gov/msl/spacecraft/instruments/summary/

Ice Sheets Covered Southern Highlands of Early Mars (Astronomy / Planetary Science)

The southern highlands of Mars are dissected by hundreds of ancient valley networks (3.9-3.5 billion years old), which are evidence that water once sculpted the Martian surface. According to new research, these valley networks were carved by water melting beneath glacial ice, not by free-flowing rivers as previously thought.

Fig: A view of Mars showing the planet’s northern polar ice cap. Image credit: ISRO / ISSDC / Emily Lakdawalla.

The similarity between many Martian valleys and the subglacial channels on Devon Island in the Canadian Arctic motivated Dr. Grau Galofre and colleagues to conduct this new study.

Fig: A glacial valley network on Mars. Image credit: Grau Galofre et al.

In the study, the scientists analyzed 10,276 Martian valley segments, using a novel algorithm to infer their underlying erosion processes.

They used data from the Mars Orbiter Laser Altimeter (MOLA) instrument on NASA’s Mars Global Surveyor spacecraft and the High Resolution Stereo Camera (HRSC) on ESA’s Mars Express orbiter.

These results are the first evidence for extensive subglacial erosion driven by channelized meltwater drainage beneath an ancient ice sheet on Mars. The findings demonstrated that only a fraction of valley networks match patterns typical of surface water erosion, which is in marked contrast to the conventional view.

Using the geomorphology of the Martian surface to rigorously reconstruct the character and evolution of the planet in a statistically meaningful way is, frankly, revolutionary.

Fig: Distribution of Martian valley networks (purple) and those analyzed (white) by Grau Galofre et al. Image credit: Grau Galofre et al, doi: 10.1038/s41561-020-0618-x.

The team’s theory also helps explain how the Martian valleys would have formed 3.8 billion years ago on a planet that is further away from the Sun than Earth, during a time when the Sun was less intense.

Climate modeling predicts that Mars’ ancient climate was much cooler during the time of valley network formation. They tried to put everything together and came up with a hypothesis that hadn’t really been considered: that channels and valleys networks can form under ice sheets, as part of the drainage system that forms naturally under an ice sheet when there’s water accumulated at the base.

These environments would also support better survival conditions for possible ancient life on Mars.

A sheet of ice would lend more protection and stability of underlying water, as well as providing shelter from solar radiation in the absence of a magnetic field — something Mars once had, but which disappeared billions of years ago.


References: Anna Grau Galofre, A. Mark Jellinek & Gordon R. Osinski, “Valley formation on early Mars by subglacial and fluvial erosion”, Nature Geoscience, published online August 3, 2020; doi: 10.1038/s41561-020-0618-x ; Link: https://www.nature.com/articles/s41561-020-0618-x