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(6 August 2020 – NASA Goddard) Vast areas of the Martian night sky pulse in ultraviolet light, according to images from NASA’s MAVEN spacecraft. The results are being used to illuminate complex circulation patterns in the Martian atmosphere.

Mars’ nightside atmosphere glows and pulsates in this data animation from MAVEN spacecraft observations. Green-to-white false color shows the enhanced brightenings on Mars’ ultraviolet “nightglow” measured by MAVEN’s Imaging UltraViolet Spectrograph at about 70 kilometers (approximately 40 miles) altitude. A simulated view of the Mars globe is added digitally for context, with ice caps visible at the poles. Three nightglow brightenings occur over one Mars rotation, the first much brighter than the other two. All three brightenings occur shortly after sunset, appearing on the left of this view of the night side of the planet. The pulsations are caused by downwards winds which enhance the chemical reaction creating nitric oxide which causes the glow. Months of data were averaged to identify these patterns, indicating they repeat nightly. (courtesy: NASA/MAVEN/Goddard Space Flight Center/CU/LASP)

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

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

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

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

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

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

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

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

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Thales Alenia Space will provide the IRIS altimeter for the Copernicus CRISTAL mission

Thales Alenia Space will provide the IRIS altimeter for the

(21 September 2020 – Thales) Thales Alenia Space has today signed a close to €88 million contract with Airbus Defence and Space, prime contractor of the satellite, to develop the two IRIS flight models (Interferometric Radar Altimeter for Ice and Snow) of the Copernicus polaR Ice and Snow Topography ALtimeter (CRISTAL) mission.

The CRISTAL mission is part of the expansion of the Copernicus Space Component programme of the European Space Agency, ESA, in partnership with the European Commission. The European Copernicus flagship programme provides Earth observation and in situ data and a broad range of services for environmental monitoring and protection, climate monitoring, natural disaster assessment to improve the quality of life of European citizens.

The CRISTAL satellite will carry, for the first-time, a dual-frequency Ku/Ka bands radar altimeter to measure and monitor sea-ice thickness and overlying snow depth. Measurements of sea-ice thickness will support maritime operations and they will help in the planning of activities in the polar regions. IRIS will also measure and monitor changes in the height of ice sheets and glaciers around the world, thanks to its interferometric radar mode. IRIS will significantly improve the measurement accuracy of its predecessor SIRAL-2 (a Ku band only altimeter on board ESA’s CryoSat-2 Earth Explorer mission) thanks to the dual frequency operation and by adding the measurement of sea surface height as part of the mission objectives. The CRISTAL global mission is essential to better understand and monitor Earth climate in a context of the rapid climate change.

CRISTAL (courtesy: Airbus Defence and Space)

Hervé Derrey, CEO of Thales Alenia Space declared: “By providing the IRIS altimeter onboard CRISTAL, Thales Alenia Space is pleased to contribute to improve the data already provided by SIRAL-2 on board Cryosat and ensure the continuity of ice monitoring. Polar regions have a real influence on patterns of global climate, thermohaline circulation, and the planetary energy balance. A long-term program to monitor Earth polar ice, ocean and snow topography is therefore of the utmost interest to both operational and scientific users of Arctic and Antarctic measurements.”

Marc-Henri Serre, VP Observation and Science domain, at Thales Alenia Space in France added: “Thales Alenia Space will bring all its expertise and long-standing heritage on space altimetry, and its flight proven heritage acquired with SIRAL-2 to serve this crucial mission to understand and monitor the climate”.

The IRIS altimeter is designed and it will be built from the legacy of several altimeter programs of the Thales Alenia Space product line, including SIRAL-2, Poseidon 4 on board Sentinel-6/Jason-CS, Alti-Ka on the CNES/ISRO satellite, and KaRIn on board the CNES/JPL SWOT satellite. Thales Alenia Space is also the first to have flown an interferometric SAR altimeter (SIRAL) offering a unique expertise in interferometric radar electronics and interferometric antennas.

About industrial contributions for CRISTAL

Thales Alenia Space in France is prime of the IRIS altimeter, with contribution from Thales Alenia Space in Belgium for the Ku and Ka band Solid State Power Amplifiers power supply, Thales Alenia Space in Italy for the Ultra stable Oscillator. Thales Alenia Space in Spain will provide the S-Band transponder (SBT) of the CRISTAL satellite.

Thales Alenia Space: world leader in space altimetry

Thales Alenia Space is a world leader in space altimetry, a technique that lets us study sea surface height, sea ice thickness and river and lake levels, as well as land, ice sheet and seabed topography. The company has provided a whole host of instruments for oceanography, like the Poseidon altimeters on the Topex-Poseidon and Jason 1, 2 and 3 missions for the CNES. Thales Alenia Space also built the AltiKa Ka-band altimeter for the French-Indian SARAL oceanography satellite, and the SIRAL 2 very-high-resolution SAR (synthetic aperture radar) altimeter on ESA’s Cryosat-2 satellite, capable of measuring variations in sea ice thickness and continental ice mass balance with unprecedented accuracy. In addition, Thales Alenia Space supply the SRAL SAR altimeters for Sentinel-3, the SWIM altimeter on the CFOSat satellite for CNES, which measures wave spectra, and the SADKO altimeters on Russia’s GEO-IK satellites.

About Thales Alenia Space

Drawing on over 40 years of experience and a unique combination of skills, expertise and cultures, Thales Alenia Space delivers cost-effective solutions for telecommunications, navigation, Earth observation, environmental management, exploration, science and orbital infrastructures. Governments and private industry alike count on Thales Alenia Space to design satellite-based systems that provide anytime, anywhere connections and positioning, monitor our planet, enhance management of its resources, and explore our Solar System and beyond. Thales Alenia Space sees space as a new horizon, helping to build a better, more sustainable life on Earth. A joint venture between Thales (67%) and Leonardo (33%), Thales Alenia Space also teams up with Telespazio to form the parent companies’ Space Alliance, which offers a complete range of services. Thales Alenia Space posted consolidated revenues of approximately 2.15 billion euros in 2019 and has around 7,700 employees in nine countries.

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Plans underway for new polar ice and snow topography mission

Plans underway for new polar ice and snow topography mission

(21 September 2020 – ESA) Monitoring the cryosphere is essential to fully assess, predict and adapt to climate variability and change. Given the importance of this fragile component of the Earth system, today ESA, along with Airbus Defence and Space and Thales Alenia Space, have signed a contract to develop the Copernicus Polar Ice and Snow Topography Altimeter mission, known as CRISTAL.

Copernicus Polar Ice and Snow Topography Altimeter (CRISTAL) mission (courtesy: Airbus)

With a launch planned in 2027, the CRISTAL mission will carry, for the first time on a polar mission, a dual-frequency radar altimeter, and microwave radiometer, that will measure and monitor sea-ice thickness, overlying snow depth and ice-sheet elevations.

These data will support maritime operations in the polar oceans and contribute to a better understanding of climate processes. CRISTAL will also support applications related to coastal and inland waters, as well as providing observations of ocean topography.

The mission will ensure the long-term continuation of radar altimetry ice elevation and topographic change records, following on from previous missions such as ESA’s Earth Explorer CryoSat mission and other heritage missions.

With a contract secured worth € 300 million, Airbus Defence and Space has been selected to develop and build the new CRISTAL mission, while Thales Alenia Space has been chosen as the prime contractor to develop its Interferometric Radar Altimeter for Ice and Snow (IRIS).

ESA’s Director of Earth Observation Programmes, Josef Aschbacher, says, “I am extremely pleased to have the contract signed so we can continue the development of this crucial mission. It will be critical in monitoring climate indicators, including the variability of Arctic sea ice, and ice sheet and ice cap melting.”

The contract for CRISTAL is the second out of the six new high-priority candidate missions to be signed – after the Copernicus Carbon Dioxide Monitoring mission (CO2M) in late-July. The CRISTAL mission is part of the expansion of the Copernicus Space Component programme of ESA, in partnership with the European Commission.

The European Copernicus flagship programme provides Earth observation and in situ data, as well as a broad range of services for environmental monitoring and protection, climate monitoring and natural disaster assessment to improve the quality of life of European citizens.

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Astronomers solve mystery of how planetary nebulae are shaped

Astronomers solve mystery of how planetary nebulae are shaped

(17 September 2020 – Center for Astrophysics | Harvard & Smithsonian) Following extensive observations of stellar winds around cool evolved stars scientists have figured out how planetary nebulae get their mesmerizing shapes.

The findings, published in Science, contradict common consensus, and show that not only are stellar winds aspherical, but they also share similarities with planetary nebulae.

Gallery of stellar winds around cool aging stars, showing a variety of morphologies, including disks, cones, and spirals. The blue color represents material that is coming towards you, red is material that is moving away from you. Image 8, in particular, shows the stellar wind of R Aquilae, which resembles the structure of rose petals. (courtesy: L. Decin, ESO/ALMA)

An international team of astronomers focused their observations on stellar winds—particle flows—around cool red giant stars, also known as asymptotic giant branch (AGB) stars. “AGB stars are cool luminous evolved stars that are in the last stages of evolution just before turning into a planetary nebula,” said Carl Gottlieb, an astronomer at the Center for Astrophysics | Harvard & Smithsonian, and a co-author on the paper. “Through their winds, AGB stars contribute about 85% of the gas and 35% of the dust from stellar sources to the Galactic Interstellar Medium and are the dominant suppliers of pristine building blocks of interstellar material from which planets are ultimately formed.”

Despite being of major interest to astronomers, a large, detailed collection of observational data for the stellar winds surrounding AGB stars—each made using the exact same method—was lacking prior to the study, which resulted in a long-standing scientific misconception: that stellar winds have an overall spherical symmetry. “The lack of such detailed observational data caused us to initially assume that the stellar winds have an overall spherical geometry, much like the stars they surround,” said Gottlieb. “Our new observational data shapes a much different story of individual stars, how they live, and how they die. We now have an unprecedented view of how stars like our Sun will evolve during the last stages of their evolution.”

Observations with the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile revealed something strange: the shape of the stellar winds didn’t conform with scientific consensus. “We noticed these winds are anything but round,” said Professor Leen Decin of KU Leuven University in Belgium, and the lead author on the paper. “Some of them are actually quite similar to planetary nebulae.” The new findings may have a significant impact on calculations of galactic and stellar evolution, most pointedly for the evolution of Sun-like stars. “Our findings change a lot,” said Decin. “Since the complexity of stellar winds was not accounted for in the past, any previous estimate of the mass-loss rate of old stars could be wrong by up to a factor of 10.”

The observations revealed many different shapes, further connecting stellar wind formation to that of planetary nebulae. “The winds we observed exhibit various shapes that are similar to planetary nebulae,” said Gottlieb. “Some are disk-like, while others are shaped like eyes, spiral structures, and even arcs.”

Astronomers quickly realized that the shapes weren’t formed randomly, and that companions—low-mass stars and heavy planets—in the vicinity of the AGB stars were influencing the shapes and patterns. “Just like a spoon that you stir in a cup of coffee with some milk can create a spiral pattern, the companion sucks material towards it as it revolves around the star and shapes the stellar wind,” said Decin. “All of our observations can be explained by the fact that the stars have a companion.”

In addition, the study provides a strong foundation for understanding Sun-like stars and the future of the Sun itself. “In about five billion years, the Sun will become more luminous,” said Gottlieb. “Its radius will expand to a length that is comparable to the current distance between the Sun and Earth, and it will enter the AGB phase.” Decin added, “Jupiter or even Saturn—because they have such a big mass—are going to influence whether the Sun spends its last millennia at the heart of a spiral, a butterfly or any of the other entrancing shapes we see in planetary nebulae today. Our current simulations predict that Jupiter and Saturn will create a weak spiral structure in the wind of the Sun once it is an AGB star.”

About Center for Astrophysics | Harvard & Smithsonian

Headquartered in Cambridge, Mass., the Center for Astrophysics | Harvard & Smithsonian (CfA) is a collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

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