Category Archives: Planetary Science

Helium Structures In Sun’s Atmosphere Were Found By NASA Sounding Rocket (Astronomy / Planetary Science)

In 2009, NASA launched a sounding rocket investigation to measure helium in the extended solar atmosphere—the first time we’ve gathered a full global map. The results, recently published in Nature Astronomy, are helping us better understand our space environment.

Fig: A composite image of the Sun showing the hydrogen (left) and helium (center and right) in the low corona. The helium at depletion near the equatorial regions is evident. Credit: NASA

Previously, when measuring ratios of helium to hydrogen in the solar wind as it reaches Earth, observations have found much lower ratios than expected. Scientists suspected the missing helium might have been left behind in the Sun’s outermost atmospheric layer—the corona—or perhaps in a deeper layer. Discovering how this happens is key to understanding how the solar wind is accelerated.

To measure the amount of atmospheric helium and hydrogen, NASA’s Helium Resonance Scattering in the Corona and Heliosphere, or HERSCHEL, sounding rocket took images of the solar corona. Led by the Naval Research Lab in Washington, D.C., HERSCHEL was an international collaboration with the Osservatorio Astrofisico di Torino in Italy and the Institute d’Astrophysique Spatiale in France.

HERSCHEL’s observations showed that helium wasn’t evenly distributed around the corona. The equatorial region had almost no helium while the areas at mid latitudes had the most. Comparing with images from ESA/NASA’s Solar and Heliospheric Observatory (SOHO), the scientists were able to show the abundance at the mid latitudes overlaps with where Sun’s magnetic field lines open out into the solar system.

This shows that the ratio of helium to hydrogen is strongly connected with the magnetic field and the speed of the solar wind in the corona. The equatorial regions, which had low helium abundance measurements, matched measurements from the solar wind near Earth. This points to the solar atmosphere being more dynamic than scientists thought.

The HERSCHEL sounding rocket investigation adds to a body of work seeking to understand the origin of the slow component of the solar wind. HERSCHEL remotely investigates the elemental composition of the region where the solar wind is accelerated, which can be analyzed in tandem with in situ measurements of the inner solar system, such as those of the Parker Solar Probe. While the heat of the Sun is enough to power the lightest element—ionized hydrogen protons—to escape the Sun as a supersonic wind, other physics must help power the acceleration of heavier elements such as helium. Thus, understanding elemental abundance in the Sun’s atmosphere, provides additional information as we attempt to learn the full story of how the solar wind is accelerated.

In the future, scientists plan to take more observations to explain the difference in abundances. Two new instruments—Metis and EUI on board ESA/NASA’s Solar Orbiter—are able to make similar global abundance measurements and will to help provide new information about the helium ratio in the corona.

References: John D. Moses et al. Global helium abundance measurements in the solar corona, Nature Astronomy (2020). DOI: 10.1038/s41550-020-1156-6

About 35 Years-Long, Deep Gaint Cloud Disruption Discovered On Venus (Astronomy / Planetary Science)

A study with the participation of the Instituto de Astrofísica e Ciências do Espaço (IA) described that, a planetary-scale cloud discontinuity has been periodically lashing the depths of the thick blanket of clouds on Venus for at least 35 years.

Fig: Example of undulations behind the discontinuity on the night side on 15th April 2016. Credit: Javier Peralta/JAXA-Planet C team

In the cloudy heavens of Venus, consisting mostly of carbon dioxide with clouds made of droplets of sulphuric acid, a giant atmospheric disruption not yet seen elsewhere in the solar system has been rapidly moving at around 50 kilometers above the hidden surface, and has gone unnoticed for at least 35 years. Its discovery is reported in a study now published in the Geophysical Research Letters and had the contribution of Pedro Machado, of Instituto de Astrofísica e Ciências do Espaço (IA) and Faculdade de Ciências da Universidade de Lisboa (Ciências ULisboa).

This planet-wide cloud discontinuity can sometimes extend as far as 7500 kilometers, across the equator, from 30º north to 40º south, and happens at the lower cloud level, at altitudes between 47.5 and 56.5 kilometers. The researchers discovered that since at least 1983, this wall of acid clouds is periodically swiping the solid globe over five days at about 328 kilometers per hour.

The study was led by the Japanese space agency JAXA, which first spotted what looked like an atmospheric wave, but of planet-sized proportions. This was hinted from the infrared images of great detail taken from the nightside of the planet by JAXA’s Venus orbiter Akatsuki, which probed the mid and lower layers of the atmosphere.

IA contributed under its long research program studying Venus’ winds, but also with follow-up observations with NASA’s Infrared Telescope Facility (IRTF), in Hawaii, coordinated with new observations made from space with the Akatsuki orbiter.

Fig: Pattern of cloud disruption seen in infrared images taken by the Japanese space agency-JAXA Akatsuki Venus orbiter in 2016. Credit: Javier Peralta/JAXA-Planet C team

While researchers have observed other giant cloud patterns in the atmosphere of Venus, such as the Y wave or the 10,000-kilometers-long, bow-shaped stationary wave in the upper clouds, this is the first serious candidate for a planetary wave found at low altitudes.

The deep region in the atmosphere where this new disruption was discovered is responsible for the rampant greenhouse effect that retains the heat and keeps the surface at a temperature of 465 degrees Celsius, hot enough to melt lead. Planetary-scale waves such as this might help establish a link between the surface and the dynamics of the Venusian atmosphere as a whole, which, to an extent, is still a mystery.

Fig: A fast disruption dominates the deeper clouds of Venus at the equatorial region, as observed in the left-bottom time composite made with infrared2.26-μm images the nightside of Venus acquired between 25-28 of August 2016 by the camera IR2 onboard JAXA’s Akatsuki orbiter. The long-term evolution of the disruption from March 2016 to December 2018 is also shown as a sequence of smaller images. Credit: Planet-C Project Team, NASA, IRTF

However, the mechanism that ignited and maintains the long-lasting phenomenon with cycles of varying intensity is still unknown, despite computer simulations trying to mimic it. According to the researchers, this atmospheric disruption is a new meteorological phenomenon, unseen on other planets, and it is thus difficult to provide a confident physical interpretation.

While it will be the focus of future research, the authors suggest that this disruption may be the physical manifestation of an atmospheric wave of the Kelvin type, propagating and trapped about the equator. Kelvin waves are a class of atmospheric gravity waves that share important common features with this disruption. For instance, they propagate in the same direction as the super-rotating winds and with no apparent effect on the meridional winds, the winds blowing from the equator toward the poles.

Kelvin waves can interact with other types of atmospheric waves like the ones that naturally occur as a result of the rotation of the planet, the Rossby waves. These may cause the transport of energy of the super-rotation to the equator.

Revisiting images taken as far back as 1983, the researchers were able to confirm the presence of the same features.

References: (1) J. Peralta et al. A Long‐Lived Sharp Disruption on the Lower Clouds of Venus, Geophysical Research Letters (2020). DOI: 10.1029/2020GL087221

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:

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:

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).

Juno Discovers ‘Shallow Lightning’ on Jupiter (Astronomy / Planetary Science)

According to a new analysis of data collected by the Stellar Reference Unit instrument onboard NASA’s Juno spacecraft, an unexpected form of electrical discharge, ‘shallow lightning’ originates from Jovian clouds containing an ammonia-water solution.

Fig: This illustration uses data obtained by NASA’s Juno mission to depict high-altitude electrical storms on Jupiter. Juno’s Stellar Reference Unit camera detected unusual lightning flashes on Jupiter’s dark side during the spacecraft’s close flybys of the planet. Image credit: NASA / JPL-Caltech / SwRI / MSSS / Gerald Eichstädt.

Since NASA’s Voyager mission first saw Jovian lightning flashes in 1979, it has been thought that the planet’s lightning is similar to Earth’s, occurring only in thunderstorms where water exists in all its phases — ice, liquid, and gas.

At Jupiter this would place the storms around 45 to 65 km (28-40 miles) below the visible clouds, with temperatures that hover around 0 degrees Celsius (32 degrees Fahrenheit).

Voyager, and all other missions to the gas giant prior to Juno, saw lightning as bright spots on Jupiter’s cloud tops, suggesting that the flashes originated in deep water clouds.

But lightning flashes observed on Jupiter’s dark side by Juno’s Stellar Reference Unit tell a different story.

Ammonia is the key. While there is water and other chemical elements such as molecular hydrogen and helium in Jupiter’s clouds, ammonia is the antifreeze that keeps water in those upper atmospheric clouds from freezing entirely.

The collision of the falling droplets of mixed ammonia and water with suspended water-ice particles constitutes a way to separate charge and produce cloud electrification — resulting in lightning storms in the upper atmosphere.

The spatial resolution of some cameras allowed investigators to confirm 22 flashes with HWHM greater than 42 kilometres, and to estimate one with an HWHM of 37 to 45 kilometres. These flashes, with optical energies comparable to terrestrial ‘superbolts’—of (0.02–1.6) × 10^10 joules—have been interpreted as tracers of moist convection originating near the 5-bar level of Jupiter’s atmosphere (assuming photon scattering from points beneath the clouds).

Previous observations of lightning have been limited by camera sensitivity, distance from Jupiter and long exposures (about 680 milliseconds to 85 seconds), meaning that some measurements were probably superimposed flashes reported as one.

Authors reported optical observations of lightning flashes by the Juno spacecraft with energies of approximately 10^5–10^8 joules, flash durations as short as 5.4 milliseconds and inter-flash separations of tens of milliseconds, with typical terrestrial energies.

The flash rate is about 6.1 × 10^−2 flashes per square kilometre per year, more than an order of magnitude greater than hither to seen. Several flashes are of such small spatial extent that they must originate above the 2-bar level, where there is no liquid water. This implies that multiple mechanisms for generating lightning on Jupiter need to be considered for a full understanding of the planet’s atmospheric convection and composition.

References: (1) H.N. Becker et al. 2020. Small lightning flashes from shallow electrical storms on Jupiter. Nature 584, 55-58; doi: 10.1038/s41586-020-2532-1 link:

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:

Perseverance Launches to Hunt for Signs of Ancient Martian Life (Planetary Science / Astronomy)

NASA’s Mars 2020 Perseverance rover and Ingenuity helicopter launched on a United Launch Alliance Atlas V 541 rocket from Space Launch Complex 41 at Cape Canaveral Air Force Station at 7:50 a.m. EDT on July 30, 2020.

The Perseverance rover mission will address high-priority science goals for Mars exploration.

Developed under NASA’s Mars Exploration Program, it will seek signs of past microbial life and characterize the planet’s climate and geology.

It will also collect samples of Martian rocks and dust for a future Mars Sample Return mission to Earth, while paving the way for human exploration of the Red Planet.

Perseverance will land in Jezero Crater on Mars on February 18, 2021.

Home to a lake billions of years ago, Jezero isn’t a typical Mars crater.

The car-sized Perseverance is also the largest, heaviest robotic Mars rover NASA has built.

The rover is about 3 m (10 feet) long not including the robotic arm, 2.7 m (9 feet) wide and 2.1 m (7 feet) tall. But at 1,025 kg (2,260 pounds), it weighs less than a compact car.

Its robotic arm is equipped with a rotating turret, which includes a rock drill, science instruments and a camera.

But while Perseverance’s arm is 2.1 m (7 feet) long, just like Curiosity’s, its turret weighs more — 45 kg (99 pounds) — because it carries larger instruments and a larger drill for coring. The drill will cut intact rock cores, and they’ll be placed in sample tubes via a complex storage system.

Perseverance also has a six-wheel, rocker-bogie design derived from all of NASA’s Mars rovers to date that helps to maintain a relatively constant weight on each of the rover’s wheels and minimizes tilt.

The wheels are slightly narrower and taller than Curiosity’s but are similarly machined out of a rigid, lightweight aluminum alloy.

Both Curiosity and Perseverance have wheels lined with grousers — raised treads that are specially designed for the Martian desert.

Fig: This artist’s concept depicts NASA’s Mars rover Perseverance on the surface of the Red Planet. Image credit: NASA / JPL-Caltech.

Perseverance is carrying seven different scientific instruments:

(i) Mastcam-Z is an advanced camera system with panoramic and stereoscopic imaging capability with the ability to zoom;

(ii) SuperCam is an instrument that can provide imaging, chemical composition analysis, and mineralogy at a distance;

(iii) Planetary Instrument for X-ray Lithochemistry (PIXL) is an X-ray fluorescence spectrometer and high-resolution imager, which will map the fine-scale elemental composition of Martian surface materials;

(iv) Scanning Habitable Environments with Raman & Luminescence for Organics and Chemicals (SHERLOC) is a spectrometer that will provide fine-scale imaging and uses an ultraviolet (UV) laser to map mineralogy and organic compounds;

(v) The Mars Oxygen In-Situ Resource Utilization Experiment (MOXIE) is a technology demonstration that will produce oxygen from Martian atmospheric carbon dioxide;

(vi) Mars Environmental Dynamics Analyzer (MEDA) is a set of sensors that will provide measurements of temperature, wind speed and direction, pressure, relative humidity, and dust size and shape;

(vii) Radar Imager for Mars’ Subsurface Experiment (RIMFAX) is a ground-penetrating radar that will provide centimeter-scale resolution of the geologic structure of the subsurface.

Another special feature on Perseverance can be found on the aft crossbeam: a plate that contains three silicon chips stenciled with the names of approximately 10.9 million people from around the world who participated in the online ‘Send Your Name to Mars’ campaign from May to September 2019.

The fingernail-sized chips also contain the essays of 155 finalists in NASA’s ‘Name the Rover’ essay contest.

The chips share space on an anodized plate with a laser-etched graphic depicting Earth and Mars joined by the star that gives light to both and a message in Morse code in the Sun’s rays: ‘Explore as one.’

Perseverance is also bringing a twin-rotor, solar-powered helicopter named Ingenuity to test out aerial flight on another planet for the first time.

Perseverance is ferrying 23 cameras to the Red Planet — the most ever flown in the history of deep-space exploration. Two cameras are installed on the Ingenuity helicopter.

References: (1) (2) (3)

Moon May Be 85 Million Years Younger than Previously Thought (Astronomy)

According to a new modeling study by M. Maurice & colleagues, Earth’s only natural satellite formed 4.425 billion years ago — around 85 million years later than previous estimates..

Fig: When the Moon formed into a sphere approximately 1,700 km in radius 4.425 billion years ago, its interior heated up considerably due to the energy released when it accreted. The rock melted and an ocean of magma, possibly more than 1,000 km deep, formed. Later, light rocks crystallized, which rose to the surface and formed a first crust on the Moon. This crust insulated the Moon from space, and the magma ocean beneath it cooled down slowly. Around 200 million years would pass before the Moon completely solidified. Image credit: NASA’s Goddard Space Flight Center.

According to the giant impact hypothesis, the Moon was created out of the debris left over from a catastrophic collision between the proto-Earth and a Mars-sized protoplanet called Theia.

This collision produced a lunar magma ocean and initiated the last event of core segregation on Earth. However, the timing of these events remains uncertain.

The scientists determined when the Moon was formed using a new, indirect method & they demonstrated that the lunar magma ocean quickly began to solidify and formed a crust of floating, lightweight crystals at the surface — its ‘interface’ with the cold space.

But under this insulating crust, which slowed down the further cooling and solidification of the magma ocean, the Moon remained molten for a long time.

Until now, scientists were unable to determine how long it took for the magma ocean to crystallize completely, which is why they could not conclude when the Moon originally formed.

To calculate the lifetime of the Moon’s magma ocean, the authors used a new computer model, which for the first time comprehensively considered the processes involved in the solidification of the magma.

& their results from the model showed that the Moon’s magma ocean was long-lived and took almost 200 million years to completely solidify into mantle rock. The time scale is much longer than calculated in previous studies. Older models gave a solidification period of only 35 million years.

To determine the age of the Moon, the team calculated how the composition of the magnesium- and iron-rich silicate minerals that formed during the solidification of the magma ocean changed over time.

The researchers discovered a drastic change in the composition of the remaining magma ocean as solidification progressed.

This finding is significant because it allowed them to link the formation of different types of rock on the Moon to a certain stage in the evolution of its magma ocean.

By comparing the measured composition of the Moon’s rocks with the predicted composition of the magma ocean from their model, they were able to trace the evolution of the ocean back to its starting point, the time at which the Moon was formed.

The results showed that the Moon was formed 4.425 billion years ago.

This age is in remarkable agreement with an age previously determined for the formation of Earth’s metallic core with the uranium-lead method, the point at which the formation of the Earth was completed.

References: M. Maurice, N. Tosi, S. Schwinger, D. Breuer and T. Kleine, “A long-lived magma ocean on a young Moon”, Science Advances 10 Jul 2020:
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