Success! Japanese Spacecraft Arrives at Venus 5 Years After 1st Try (Dec 2015 Space.com)

A Japanese Venus probe took advantage of its long-awaited second chance.
Japan's Akatsuki spacecraft has arrived in orbit around Venus, five years after an engine failure scuttled its first attempt, Japanese Aerospace Exploration Agency (JAXA) officials announced today (Dec. 9).

The $300 million Akatsuki mission launched in May 2010 along with JAXA's IKAROS (Interplanetary Kite-craft Accelerated by Radiation Of the Sun) spacecraft, which became the first probe ever to deploy and use a solar sail in interplanetary space. .

Akatsuki was originally supposed to enter Venus orbit on Dec. 6, 2010, then study the planet's clouds, weather and atmosphere from above for at least two years to learn more about how the world became so hot and seemingly inhospitable to life. But the spacecraft's main engine conked out during a crucial orbit-insertion burn, and Akatsuki went zooming off into space.
The spacecraft — whose name means "Dawn" in Japanese — had been circling the sun for five years, waiting for another shot at Venus. That shot came exactly five years to the day after the first opportunity.  
On Sunday (Dec. 6), Akatsuki fired its small attittude-control thrusters for 20 minutes to achieve Venus orbit (its main engine was pronounced dead long ago). After a few days of calculations and computations, mission controllers have now determined that the maneuver worked.

"The orbit period is 13 days and 14 hours. We also found that the orbiter is flying in the same direction as that of Venus's rotation," JAXA officials wrote in a statement today. "The Akatsuki is in good health."
Akatsuki's current path takes it as close as 250 miles (400 kilometers) to Venus, and as far away as 273,000 miles (440,000 km), officials added. This orbit is much more elliptical than the one Akatsuki was supposed to achieve five years ago, which featured a period of 30 hours and an apoapsis (most distant point from Venus) of 50,000 miles (80,000 km) or so.
Akatsuki's handlers will soon deploy and test three of the probe's six instruments, to make sure they're working properly — the other three are already known to be in good condition — and then conduct initial observations with all of this scientific gear for about three months, JAXA officials said.
At the same time, Akatsuki will maneuver to a less-elliptical final science orbit with a period of about nine days and an apoapsis around 193,000 miles (310,000 km). The probe should achieve that orbit, and commence regular operations, by April 2016. 

Despite the long delay, the drama and the highly elliptical orbit, Akatsuki should still be able to accomplish most of its science goals, JAXA officials have said.


JAXA Mission website; http://global.jaxa.jp/projects/sat/planet_c/index.html

NASA Telescopes Detect Jupiter-Like Storm on Small Star

Astronomers have discovered what appears to be a tiny star with a giant, cloudy storm, using data from NASA's Spitzer and Kepler space telescopes. The dark storm is akin to Jupiter's Great Red Spot: a persistent, raging storm larger than Earth.
"The star is the size of Jupiter, and its storm is the size of Jupiter's Great Red Spot," said John Gizis of the University of Delaware, Newark. "We know this newfound storm has lasted at least two years, and probably longer." Gizis is the lead author of a new study appearing in The Astrophysical Journal.
While planets have been known to have cloudy storms, this is the best evidence yet for a star that has one. The star, referred to as W1906+40, belongs to a thermally cool class of objects called L-dwarfs. Some L-dwarfs are considered stars because they fuse atoms and generate light, as our sun does, while others, called brown dwarfs, are known as "failed stars" for their lack of atomic fusion.
The L-dwarf in the study, W1906+40, is thought to be a star based on estimates of its age (the older the L-dwarf, the more likely it is a star). Its temperature is about 3,500 degrees Fahrenheit (2,200 Kelvin). That may sound scorching hot, but as far as stars go, it is relatively cool. Cool enough, in fact, for clouds to form in its atmosphere.
"The L-dwarf's clouds are made of tiny minerals," said Gizis.
Spitzer has observed other cloudy brown dwarfs before, finding evidence for short-lived storms lasting hours and perhaps days.
In the new study, the astronomers were able to study changes in the atmosphere of W1906+40 for two years. The L-dwarf had initially been discovered by NASA's Wide-field Infrared Survey Explorer in 2011. Later, Gizis and his team realized that this object happened to be located in the same area of the sky where NASA's Kepler mission had been staring at stars for years to hunt for planets.
Kepler identifies planets by looking for dips in starlight as planets pass in front of their stars. In this case, astronomers knew observed dips in starlight weren't coming from planets, but they thought they might be looking at a star spot -- which, like our sun's "sunspots," are a result of concentrated magnetic fields. Star spots would also cause dips in starlight as they rotate around the star.
Follow-up observations with Spitzer, which detects infrared light, revealed that the dark patch was not a magnetic star spot but a colossal, cloudy storm with a diameter that could hold three Earths. The storm rotates around the star about every 9 hours. Spitzer's infrared measurements at two infrared wavelengths probed different layers of the atmosphere and, together with the Kepler visible-light data, helped reveal the presence of the storm.
While this storm looks different when viewed at various wavelengths, astronomers say that if we could somehow travel there in a starship, it would look like a dark mark near the polar top of the star.
The researchers plan to look for other stormy stars and brown dwarfs using Spitzer and Kepler in the future.
"We don't know if this kind of star storm is unique or common, and we don't why it persists for so long," said Gizis.

NASA Mars Rover Curiosity Reaches Sand Dunes

NASA's Curiosity Mars rover has begun an up-close investigation of dark sand dunes up to two stories tall. The dunes are on the rover's trek up the lower portion of a layered Martian mountain.
A view of the rippled surface of what's been informally named "High Dune" is online at:
http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA20168
A wheel track exposing material beneath the surface of a sand sheet nearby is at:
http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA20169
The dunes close to Curiosity's current location are part of "Bagnold Dunes," a band along the northwestern flank of Mount Sharp inside Gale Crater. Observations of this dune field from orbit show that edges of individual dunes move as much as 3 feet (1 meter) per Earth year.
The rover's planned investigations include scooping a sample of the dune material for analysis with laboratory instruments inside Curiosity.
Curiosity has been working on Mars since early August 2012. It reached the base of Mount Sharp in 2014 after fruitfully investigating outcrops closer to its landing site and then trekking to the mountain. The main mission objective now is to examine successively higher layers of Mount Sharp.
For more information about Curiosity, visit:
http://mars.jpl.nasa.gov/msl

New Clues to Ceres' Bright Spots and Origins

Ceres reveals some of its well-kept secrets in two new studies in the journal Nature, thanks to data from NASA's Dawn spacecraft. They include highly anticipated insights about mysterious bright features found all over the dwarf planet's surface. In one study, scientists identify this bright material as a kind of salt. The second study suggests the detection of ammonia-rich clays, raising questions about how Ceres formed.
About the Bright Spots
Ceres has more than 130 bright areas, and most of them are associated with impact craters. Study authors, led by Andreas Nathues at Max Planck Institute for Solar System Research, Göttingen, Germany, write that the bright material is consistent with a type of magnesium sulfate called hexahydrite. A different type of magnesium sulfate is familiar on Earth as Epsom salt.
Nathues and colleagues, using images from Dawn's framing camera, suggest that these salt-rich areas were left behind when water-ice sublimated in the past. Impacts from asteroids would have unearthed the mixture of ice and salt, they say.
"The global nature of Ceres' bright spots suggests that this world has a subsurface layer that contains briny water-ice," Nathues said.
A New Look at Occator
The surface of Ceres, whose average diameter is 584 miles (940 kilometers), is generally dark -- similar in brightness to fresh asphalt -- study authors wrote. The bright patches that pepper the surface represent a large range of brightness, with the brightest areas reflecting about 50 percent of sunlight shining on the area. But there has not been unambiguous detection of water ice on Ceres; higher-resolution data are needed to settle this question.
The inner portion of a crater called Occator contains the brightest material on Ceres. Occator itself is 60 miles (90 kilometers) in diameter, and its central pit, covered by this bright material, measures about 6 miles (10 kilometers) wide and 0.3 miles (0.5 kilometers) deep. Dark streaks, possibly fractures, traverse the pit. Remnants of a central peak, which was up to 0.3 miles (0.5 kilometers) high, can also be seen.
With its sharp rim and walls, and abundant terraces and landslide deposits, Occator appears to be among the youngest features on Ceres. Dawn mission scientists estimate its age to be about 78 million years old.
Study authors write that some views of Occator appear to show a diffuse haze near the surface that fills the floor of the crater. This may be associated with observations of water vapor at Ceres by the Herschel space observatory that were reported in 2014. The haze seems to be present in views during noon, local time, and absent at dawn and dusk, study authors write. This suggests that the phenomenon resembles the activity at the surface of a comet, with water vapor lifting tiny particles of dust and residual ice. Future data and analysis may test this hypothesis and reveal clues about the process causing this activity.
"The Dawn science team is still discussing these results and analyzing data to better understand what is happening at Occator," said Chris Russell, principal investigator of the Dawn mission, based at the University of California, Los Angeles.
The Importance of Ammonia
In the second Nature study, members of the Dawn science team examined the composition of Ceres and found evidence for ammonia-rich clays. They used data from the visible and infrared mapping spectrometer, a device that looks at how various wavelengths of light are reflected by the surface, allowing minerals to be identified.
Ammonia ice by itself would evaporate on Ceres today, because the dwarf planet is too warm. However, ammonia molecules could be stable if present in combination with (i.e. chemically bonded to) other minerals.
The presence of ammoniated compounds raises the possibility that Ceres did not originate in the main asteroid belt between Mars and Jupiter, where it currently resides, but instead might have formed in the outer solar system. Another idea is that Ceres formed close to its present position, incorporating materials that drifted in from the outer solar system - near the orbit of Neptune, where nitrogen ices are thermally stable.
"The presence of ammonia-bearing species suggests that Ceres is composed of material accreted in an environment where ammonia and nitrogen were abundant. Consequently, we think that this material originated in the outer cold solar system," said Maria Cristina De Sanctis, lead author of the study, based at the National Institute of Astrophysics, Rome.
In comparing the spectrum of reflected light from Ceres to meteorites, scientists found some similarities. Specifically, they focused on the spectra, or chemical fingerprints, of carbonaceous chondrites, a type of carbon-rich meteorite thought to be relevant analogues for the dwarf planet. But these are not good matches for all wavelengths that the instrument sampled, the team found. In particular, there were distinctive absorption bands, matching mixtures containing ammoniated minerals, associated with wavelengths that can't be observed from Earth-based telescopes.
The scientists note another difference is that these carbonaceous chondrites have bulk water contents of 15 to 20 percent, while Ceres' content is as much as 30 percent.
"Ceres may have retained more volatiles than these meteorites, or it could have accreted the water from volatile-rich material," De Sanctis said.
The study also shows that daytime surface temperatures on Ceres span from minus 136 degrees to minus 28 degrees Fahrenheit (180 to 240 Kelvin). The maximum temperatures were measured in the equatorial region. The temperatures at and near the equator are generally too high to support ice at the surface for a long time, study authors say, but data from Dawn's next orbit will reveal more details.
As of this week, Dawn has reached its final orbital altitude at Ceres, about 240 miles (385 kilometers) from the surface of the dwarf planet. In mid-December, Dawn will begin taking observations from this orbit, including images at a resolution of 120 feet (35 meters) per pixel, infrared, gamma ray and neutron spectra, and high-resolution gravity data.

NASA Juno Cam Platform Opened Up

When NASA's Juno mission arrives at Jupiter on July 4, 2016, new views of the giant planet's swirling clouds will be sent back to Earth, courtesy of its color camera, called JunoCam. But unlike previous space missions, professional scientists will not be the ones producing the processed views, or even choosing which images to capture. Instead, the public will act as a virtual imaging team, participating in key steps of the process, from identifying features of interest to sharing the finished images online.
"This is really the public's camera. We are hoping students and whole classrooms will get involved and join our team," said Scott Bolton, Juno principal investigator at the Southwest Research Institute in San Antonio.
The Juno team has kicked off the first stage of JunoCam activity with the launch of a new Web platform on the mission's website. Now and throughout the mission, amateur astronomers are invited to submit images of Jupiter from their own telescopes. These views will be the basis for online discussions about which of Jupiter's swirls, bands and spots JunoCam should image as it makes repeated, close passes over the planet. The ground-based views will be essential for identifying and tracking changes in the planet's cloud features as Juno approaches.
"In between our close Jupiter flybys, Juno goes far from the planet, and Jupiter will shrink in JunoCam's field of view to a size too small to be useful for choosing which features to capture. So we really are counting on having help from ground-based observers," said Candy Hansen, a member of the Juno science team who leads planning for the camera.
Juno will get closer to Jupiter than any previous orbiting spacecraft, giving JunoCam the best close-up views yet of the planet's colorful cloud bands. Every 14 days, the spinning, solar-powered spacecraft will dive past the planet in just a couple of hours, gathering huge amounts of science data, plus about a dozen JunoCam images. At closest approach, Juno will snap photos from only 3,100 miles (5,000 kilometers) above Jupiter's clouds.
"JunoCam will capture high-resolution color views of Jupiter's bands, but that's only part of the story," said Diane Brown, Juno program executive at NASA Headquarters in Washington. "We'll also be treated to the first-ever views of Jupiter's north and south poles, which have never been imaged before."
Unlike most spacecraft cameras, JunoCam was specially designed to work on a spinning spacecraft. Typically, spacecraft must point very precisely at their subjects while taking a picture to avoid smearing their images. Since Juno rotates twice per minute, the Juno team designed a camera that images several lines of pixels at a time, at the right speed to cancel out the rotation and avoid smear.
Previously, the best images of Jupiter were taken by NASA's two Voyager spacecraft, which flew past the planet in 1979. JunoCam's field of view is much wider than that of Voyager's narrow-angle camera. This means every JunoCam image is a kind of panorama, and its highest-resolution images will show wide swaths of clouds. The camera also benefits from decades of technology advancement, making it lighter, less power-hungry and lower in cost.
After JunoCam data arrive on Earth, members of the public will process the images to create color pictures. The Juno team successfully tested this approach when JunoCam acquired its first high-resolution views, showing our home planet during the spacecraft's Earth flyby in October 2013.
Since the mission's beginnings, JunoCam was intended almost entirely as a public outreach tool, in contrast to the spacecraft's other instruments that will address Juno's core science questions. Juno scientists will ensure JunoCam returns a few great shots of Jupiter's polar regions, but the overwhelming majority of the camera's image targets will be chosen by the public, with the data being processed by them as well.
"We want to give people an opportunity to participate with NASA, and public involvement is key to JunoCam's success," said Bolton. "This is citizen science at its best."
Information about JunoCam's new features for amateur astronomer engagement is available at:

http://www.missionjuno.swri.edu/junocam

The JunoCam Web platform will soon add a discussion section to begin identifying features of interest on the planet for JunoCam to image.
The Juno mission website, designed and developed by Radical Media since 2011, has been augmented and updated to include new features in addition to the site's interactive JunoCam section.
Launched in 2011, the Juno mission uses every known technique to probe beneath the obscuring cloud cover of Jupiter to learn more about the planet's origins, structure, atmosphere and magnetosphere.
NASA's Jet Propulsion Laboratory, Pasadena, California, manages the Juno mission for the principal investigator, Scott Bolton, of Southwest Research Institute in San Antonio. Juno is part of NASA's New Frontiers Program, which is managed at NASA's Marshall Space Flight Center in Huntsville, Alabama. Lockheed Martin Space Systems, Denver, built the spacecraft. JPL is a division of the California Institute of Technology, in Pasadena, which manages the laboratory for NASA.
For more information about Juno visit:

http://www.nasa.gov/juno
http://missionjuno.swri.edu

How a dying star spreads its seed

During their death throes, as they are running out of fuel for the nuclear furnace in their cores, giant stars swell up to enormous size and eject huge amounts of gas and dust into space. But what drives out all that material? Radiation pressure is the main suspect, the idea being that photons from the star hit the dust grains, propelling them out into space. But typical grains of interstellar dust are just too small: At about a hundred-millionth of a meter, they just don’t catch enough photons. Now, a team using an instrument called SPHERE on the European Southern Observatory’s Very Large Telescope in Chile has found the answer. SPHERE was designed to directly observe planets around other stars, so it’s equipped with a mask to blot out the light from a star so that fainter things around it can be seen. The team used the instrument to observe the surroundings of the hypergiant star VY Canis Majoris (pictured) which is up to 40 times the mass of our sun and 300,000 times as luminous. As the researchers report this week in Astronomy & Astrophysics, they found that VY Canis Majoris is surrounded by dust grains 50 times larger than normal, giving them enough surface area to be successfully pushed away by the star’s radiation pressure. This explains how the dust ends up far out in space and, after the star has exploded as a supernova and dispersed more material, provides the seed material for a later generation of stars and planets.

Loss of Carbon in Martian Atmosphere Explained

Mars is blanketed by a thin, mostly carbon dioxide atmosphere -- one that is far too thin to keep water from freezing or quickly evaporating. However, geological evidence has led scientists to conclude that ancient Mars was once a warmer, wetter place than it is today. To produce a more temperate climate, several researchers have suggested that the planet was once shrouded in a much thicker carbon dioxide atmosphere. For decades that left the question, "Where did all the carbon go?"
The solar wind stripped away much of Mars' ancient atmosphere and is still removing tons of it every day. But scientists have been puzzled by why they haven't found more carbon -- in the form of carbonate -- captured into Martian rocks. They have also sought to explain the ratio of heavier and lighter carbons in the modern Martian atmosphere.
Now a team of scientists from the California Institute of Technology and NASA's Jet Propulsion Laboratory, both in Pasadena, offer an explanation of the "missing" carbon, in a paper published today by the journal Nature Communications.
They suggest that 3.8 billion years ago, Mars might have had a moderately dense atmosphere. Such an atmosphere -- with a surface pressure equal to or less than that found on Earth -- could have evolved into the current thin one, not only minus the "missing" carbon problem, but also in a way consistent with the observed ratio of carbon-13 to carbon-12, which differ only by how many neutrons are in each nucleus.
"Our paper shows that transitioning from a moderately dense atmosphere to the current thin one is entirely possible," says Caltech postdoctoral fellow Renyu Hu, the lead author. "It is exciting that what we know about the Martian atmosphere can now be pieced together into a consistent picture of its evolution -- and this does not require a massive undetected carbon reservoir."
When considering how the early Martian atmosphere might have transitioned to its current state, there are two possible mechanisms for the removal of the excess carbon dioxide. Either the carbon dioxide was incorporated into minerals in rocks called carbonates or it was lost to space.
An August 2015 study used data from several Mars-orbiting spacecraft to inventory carbonates, showing there are nowhere near enough in the upper half mile (one kilometer) or the crust to contain the missing carbon from a thick early atmosphere during a time when networks of ancient river channels were active, about 3.8 billion years ago.
The escaped-to-space scenario has also been problematic. Because various processes can change the relative amounts of carbon-13 to carbon-12 isotopes in the atmosphere, "we can use these measurements of the ratio at different points in time as a fingerprint to infer exactly what happened to the Martian atmosphere in the past," says Hu. The first constraint is set by measurements of the ratio in meteorites that contain gases released volcanically from deep inside Mars, providing insight into the starting isotopic ratio of the original Martian atmosphere. The modern ratio comes from measurements by the SAM (Sample Analysis at Mars) instrument on NASA's Curiosity rover.
One way carbon dioxide escapes to space from Mars' atmosphere is called sputtering, which involves interactions between the solar wind and the upper atmosphere. NASA's MAVEN (Mars Atmosphere and Volatile Evolution) mission has yielded recent results indicating that about a quarter pound (about 100 grams) of particles every second are stripped from today's Martian atmosphere via this process, likely the main driver of atmospheric loss. Sputtering slightly favors loss of carbon-12, compared to carbon-13, but this effect is small. The Curiosity measurement shows that today's Martian atmosphere is far more enriched in carbon-13 -- in proportion to carbon-12 -- than it should be as a result of sputtering alone, so a different process must also be at work.
Hu and his co-authors identify a mechanism that could have significantly contributed to the carbon-13 enrichment. The process begins with ultraviolet (UV) light from the sun striking a molecule of carbon dioxide in the upper atmosphere, splitting it into carbon monoxide and oxygen. Then, UV light hits the carbon monoxide and splits it into carbon and oxygen. Some carbon atoms produced this way have enough energy to escape from the atmosphere, and the new study shows that carbon-12 is far more likely to escape than carbon-13.
Modeling the long-term effects of this "ultraviolet photodissociation" mechanism, the researchers found that a small amount of escape by this process leaves a large fingerprint in the carbon isotopic ratio. That, in turn, allowed them to calculate that the atmosphere 3.8 billion years ago might have had a surface pressure a bit less thick than Earth's atmosphere today.
"This solves a long-standing paradox," said Bethany Ehlmann of Caltech and JPL, a co-author of both today's publication and the August one about carbonates. "The supposed very thick atmosphere seemed to imply that you needed this big surface carbon reservoir, but the efficiency of the UV photodissociation process means that there actually is no paradox. You can use normal loss processes as we understand them, with detected amounts of carbonate, and find an evolutionary scenario for Mars that makes sense."