Cassini Getting Set for Dramatic “Ring-Grazing Orbits” of Saturn [Video]

A thrilling ride is about to begin for NASA’s Cassini spacecraft. Engineers have been pumping up the spacecraft’s orbit around Saturn this year to increase its tilt with respect to the planet’s equator and rings. And on Nov. 30, following a gravitational nudge from Saturn’s moon Titan, Cassini will enter the first phase of the mission’s dramatic endgame.

Launched in 1997, Cassini has been touring the Saturn system since arriving there in 2004 for an up-close study of the planet, its rings and moons. During its journey, Cassini has made numerous dramatic discoveries, including a global ocean within Enceladus and liquid methane seas on Titan.

Between Nov. 30 and April 22, Cassini will circle high over and under the poles of Saturn, diving every seven days — a total of 20 times — through the unexplored region at the outer edge of the main rings.

First Phase in Dramatic Endgame for Long-Lived Cassini Spacecraft

“We’re calling this phase of the mission Cassini’s Ring-Grazing Orbits, because we’ll be skimming past the outer edge of the rings,” said Linda Spilker, Cassini project scientist at NASA’s Jet Propulsion Laboratory, Pasadena, California. “In addition, we have two instruments that can sample particles and gases as we cross the ringplane, so in a sense Cassini is also ‘grazing’ on the rings.”

On many of these passes, Cassini’s instruments will attempt to directly sample ring particles and molecules of faint gases that are found close to the rings. During the first two orbits, the spacecraft will pass directly through an extremely faint ring produced by tiny meteors striking the two small moons Janus and Epimetheus. Ring crossings in March and April will send the spacecraft through the dusty outer reaches of the F ring.

“Even though we’re flying closer to the F ring than we ever have, we’ll still be more than 4,850 miles (7,800 kilometers) distant. There’s very little concern over dust hazard at that range,” said Earl Maize, Cassini project manager at JPL.

The F ring marks the outer boundary of the main ring system; Saturn has several other, much fainter rings that lie farther from the planet. The F ring is complex and constantly changing: Cassini images have shown structures like bright streamers, wispy filaments and dark channels that appear and develop over mere hours. The ring is also quite narrow — only about 500 miles (800 kilometers) wide. At its core is a denser region about 30 miles (50 kilometers) wide.

So Many Sights to See

Cassini’s ring-grazing orbits offer unprecedented opportunities to observe the menagerie of small moons that orbit in or near the edges of the rings, including best-ever looks at the moons Pandora, Atlas, Pan and Daphnis.

Grazing the edges of the rings also will provide some of the closest-ever studies of the outer portions of Saturn’s main rings (the A, B and F rings). Some of Cassini’s views will have a level of detail not seen since the spacecraft glided just above them during its arrival in 2004. The mission will begin imaging the rings in December along their entire width, resolving details smaller than 0.6 mile (1 kilometer) per pixel and building up Cassini’s highest-quality complete scan of the rings’ intricate structure.

The mission will continue investigating small-scale features in the A ring called “propellers,” which reveal the presence of unseen moonlets. Because of their airplane propeller-like shapes, scientists have given some of the more persistent features informal names inspired by famous aviators, including “Earhart.” Observing propellers at high resolution will likely reveal new details about their origin and structure.

And in March, while coasting through Saturn’s shadow, Cassini will observe the rings backlit by the sun, in the hope of catching clouds of dust ejected by meteor impacts.

Preparing for the Finale

During these orbits, Cassini will pass as close as about 56,000 miles (90,000 kilometers) above Saturn’s cloud tops. But even with all their exciting science, these orbits are merely a prelude to the planet-grazing passes that lie ahead. In April 2017, the spacecraft will begin its Grand Finale phase.

After nearly 20 years in space, the mission is drawing near its end because the spacecraft is running low on fuel. The Cassini team carefully designed the finale to conduct an extraordinary science investigation before sending the spacecraft into Saturn to protect its potentially habitable moons.

During its grand finale, Cassini will pass as close as 1,012 miles (1,628 kilometers) above the clouds as it dives repeatedly through the narrow gap between Saturn and its rings, before making its mission-ending plunge into the planet’s atmosphere on Sept. 15. But before the spacecraft can leap over the rings to begin its finale, some preparatory work remains.

To begin with, Cassini is scheduled to perform a brief burn of its main engine during the first super-close approach to the rings on Dec. 4. This maneuver is important for fine-tuning the orbit and setting the correct course to enable the remainder of the mission.

“This will be the 183rd and last currently planned firing of our main engine. Although we could still decide to use the engine again, the plan is to complete the remaining maneuvers using thrusters,” said Maize.

Saturn's rings were named alphabetically in the order they were discovered. The narrow F ring marks the outer boundary of the main ring system. Credits: NASA/JPL-Caltech/Space Science Institute
Saturn’s rings were named alphabetically in the order they were discovered. The narrow F ring marks the outer boundary of the main ring system.
Credits: NASA/JPL-Caltech/Space Science Institute

To further prepare, Cassini will observe Saturn’s atmosphere during the ring-grazing phase of the mission to more precisely determine how far it extends above the planet. Scientists have observed Saturn’s outermost atmosphere to expand and contract slightly with the seasons since Cassini’s arrival. Given this variability, the forthcoming data will be important for helping mission engineers determine how close they can safely fly the spacecraft.

Source: news release used in accordance with the NASA Media Guidelines.

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Strange Depression on Mars Could Harbor Life

A strangely shaped depression on Mars could be a new place to look for signs of life on the Red Planet, researchers say.

The depression was probably formed by a volcano beneath a glacier and could have been a warm, chemical-rich environment well suited for microbial life.

“We were drawn to this site because it looked like it could host some of the key ingredients for habitability—water, heat, and nutrients,” says lead author Joseph Levy, a research associate at the University of Texas Institute for Geophysics, a research unit of the Jackson School of Geosciences.

(Left) A graph charting the depth of the Hellas depression at different points, and a topographic map of the depression. (Right) A graph charting the depth of the Galaxias Fossae depression at different points, and a topographic map of the depression. (Credit: Joseph Levy/NASA)
(Left) A graph charting the depth of the Hellas depression at different points, and a topographic map of the depression. (Right) A graph charting the depth of the Galaxias Fossae depression at different points, and a topographic map of the depression. (Credit: Joseph Levy/NASA)

The depression is inside a crater perched on the rim of the Hellas basin on Mars and surrounded by ancient glacial deposits. It first caught Levy’s attention in 2009, when he noticed crack-like features on pictures of depressions taken by the Mars Reconnaissance Orbiter that looked similar to “ice cauldrons” on Earth, formations found in Iceland and Greenland made by volcanos erupting under an ice sheet. Another depression in the Galaxias Fossae region of Mars had a similar appearance.

A depression located inside a crater on the edge of the Hellas basin region of Mars. New research suggests that the depression was formed by volcanic activity beneath an ice sheet—an environment that could be suitable for microbial life. View larger. (Credit: Joseph Levy/NASA)
A depression located inside a crater on the edge of the Hellas basin region of Mars. New research suggests that the depression was formed by volcanic activity beneath an ice sheet—an environment that could be suitable for microbial life. (Credit: Joseph Levy/NASA)

“These landforms caught our eye because they’re weird looking. They’re concentrically fractured so they look like a bull’s-eye. That can be a very diagnostic pattern you see in Earth materials,” says Levy, who was a postdoctoral researcher at Portland State University when he first saw the photos of the depressions.

But it wasn’t until this year that researchers were able to more thoroughly analyze the depressions using stereoscopic images to investigate whether the depressions were made by underground volcanic activity that melted away surface ice or by an impact from an asteroid.

Study collaborator Timothy Goudge, a postdoctoral fellow at the institute, used pairs of high-resolution images to create digital elevation models of the depressions that enabled in-depth analysis of their shape and structure in 3D.

Lava and ice

“The big contribution of the study was that we were able to measure not just their shape and appearance, but also how much material was lost to form the depressions. That 3D view lets us test this idea of volcanic or impact,” Levy says.

The analysis revealed that both depressions shared an unusual funnel shape, with a broad perimeter that gradually narrowed with depth.

“That surprised us and led to a lot of thinking about whether it meant there was melting concentrated in the center that removed ice and allowed stuff to pour in from the sides. Or if you had an impact crater, did you start with a much smaller crater in the past, and by sublimating away ice, you’ve expanded the apparent size of the crater,” Levy says.

After testing formation scenarios for the two depressions, researchers found that they probably formed in different ways. The debris spread around the Galaxias Fossae depression suggests that it was the result of an impact—but the known volcanic history of the area still doesn’t rule out volcanic origins, Levy said. In contrast, the Hellas depression has many signs of volcanic origins. It lacks the surrounding debris of an impact and has a fracture pattern associated with concentrated removal of ice by melting or sublimation.

The interaction of lava and ice to form a depression would be an exciting find, Levy says, because it could create an environment with liquid water and chemical nutrients, both ingredients required for life on Earth. The Hellas depression and, to a lesser extent, the Galaxias Fossae depression, should be kept in mind when looking for habitats on Mars.

“These features do really resemble ice cauldrons known from Earth, and just from that perspective they should be of great interest,” says Gro Pedersen, a volcanologist at the University of Iceland who agrees that the depressions are promising sites for future research. He was not involved with the study,

“Both because their existence may provide information on the properties of subsurface material—the potential existence of ice—and because of the potential for revealing ice-volcano interactions.”

Researchers from Brown University and Mount Holyoke College are coauthors of the study that was supported by a NASA Mars Data Analysis Program award and was published in the journal Icarus.

Source: Republished from as a derivative work under the Attribution 4.0 International license. Original article posted to Futurity by .

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How Pluto Spray-Paints Charon Red Like a Graffiti Artist

In June 2015, when the cameras on NASA’s approaching New Horizons spacecraft first spotted the large reddish polar region on Pluto’s largest moon, Charon, mission scientists knew two things: they’d never seen anything like it elsewhere in our solar system, and they couldn’t wait to get the story behind it.

Over the past year, after analyzing the images and other data that New Horizons has sent back from its historic July 2015 flight through the Pluto system, the scientists think they’ve solved the mystery. As they detail this week in the international scientific journal Nature, Charon’s polar coloring comes from Pluto itself – as methane gas that escapes from Pluto’s atmosphere and becomes “trapped” by the moon’s gravity and freezes to the cold, icy surface at Charon’s pole. This is followed by chemical processing by ultraviolet light from the sun that transforms the methane into heavier hydrocarbons and eventually into reddish organic materials called tholins.

NASA’s New Horizons spacecraft captured this high-resolution, enhanced color view of Pluto’s largest moon, Charon, just before closest approach on July 14, 2015. Scientists have learned that reddish material in the north (top) polar region – informally named Mordor Macula – is chemically processed methane that escaped from Pluto’s atmosphere onto Charon. Credits: NASA/JHUAPL/SwRI. Click/Tap for larger image.

“Who would have thought that Pluto is a graffiti artist, spray-painting its companion with a reddish stain that covers an area the size of New Mexico?” asked Will Grundy, a New Horizons co-investigator from Lowell Observatory in Flagstaff, Arizona, and lead author of the paper. “Every time we explore, we find surprises. Nature is amazingly inventive in using the basic laws of physics and chemistry to create spectacular landscapes.”

The team combined analyses from detailed Charon images obtained by New Horizons with computer models of how ice evolves on Charon’s poles. Mission scientists had previously speculated that methane from Pluto’s atmosphere was trapped in Charon’s north pole and slowly converted into the reddish material, but had no models to support that theory.

The New Horizons team dug into the data to determine whether conditions on the Texas-sized moon (with a diameter of 753 miles or 1,212 kilometers) could allow the capture and processing of methane gas. The models using Pluto and Charon’s 248-year orbit around the sun show some extreme weather at Charon’s poles, where 100 years of continuous sunlight alternate with another century of continuous darkness. Surface temperatures during these long winters dip to -430 Fahrenheit (-257 Celsius), cold enough to freeze methane gas into a solid.

“The methane molecules bounce around on Charon’s surface until they either escape back into space or land on the cold pole, where they freeze solid, forming a thin coating of methane ice that lasts until sunlight comes back in the spring,” Grundy said. But while the methane ice quickly sublimates away, the heavier hydrocarbons created from it remain on the surface.

The models also suggested that in Charon’s springtime the returning sunlight triggers conversion of the frozen methane back into gas. But while the methane ice quickly sublimates away, the heavier hydrocarbons created from this evaporative process remain on the surface.

Sunlight further irradiates those leftovers into reddish material – called tholins – that has slowly accumulated on Charon’s poles over millions of years. New Horizons’ observations of Charon’s other pole, currently in winter darkness – and seen by New Horizons only by light reflecting from Pluto, or “Pluto-shine” – confirmed that the same activity was occurring at both poles.

“This study solves one of the greatest mysteries we found on Charon, Pluto’s giant moon,” said Alan Stern, New Horizons principal investigator from the Southwest Research Institute, and a study co-author. “And it opens up the possibility that other small planets in the Kuiper Belt with moons may create similar, or even more extensive ‘atmospheric transfer’ features on their moons.”

Source: news release used under public domain rights and the NASA Media Guidelines

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Ceres asteroid may have an ‘ice volcano’ and other signs of water, NASA mission reveals

By Monica Grady, The Open University.

The arrival of NASA’s Dawn mission at the huge asteroid “1 Ceres” in early 2015 has turned out to have been well worth waiting for. This dwarf planet is the largest body in the asteroid belt between Mars and Jupiter and was the first to be discovered. But, until recently, we have only had information from ground and space-based telescopes, which have given us tantalising glimpses of a dark, possibly water-rich object.

Now the Dawn space probe has sent back a bumper harvest of findings, summarised in six new research papers published in a special issue of the journal Science. We now have a map of Ceres that reveals unusual minerals, a surface peppered with craters, and water in the form of ice and possibly an outer atmosphere of vapour. There’s also enough uncertainty in the results to sow the seeds for future research.

The data provides a global geological map of the asteroid showing that its entire surface appears to be covered in phyllosilicates, an important group of clay minerals. Two specific clays are identified: one that is magnesium-rich, the second an ammonium-rich species. There seems to be little or no pattern to the distribution of the two minerals – they are both almost everywhere.

Dawn over Ceres

This ubiquity is what is important. The minerals could not have been formed in a local event, such as an impact into an ice-filled crater. They must have been produced by planet-wide alteration, presumably implying there must have been volumes of water. It is clear that enormous quantities of liquid water are not present on Ceres now. But the signal of water-ice has been detected in at least one crater.

Because the temperature of Ceres is relatively warm (between -93℃ and -33℃), water-ice exposed at the surface would rapidly convert into a gas in such a low-pressure environment. So the discovered traces of water-ice suggest some underground ice was recently exposed and that there must be some mechanism to explain how the surface was disturbed in this way. Some researchers think that the answer is cryovolcanism, where subsurface layers of mixed ice and minerals percolate slowly to the surface through cracks and fractures, or more swiftly following an impact. If the minerals are chlorides, then a low temperature brine can keep the subsurface layer mobile.

Ice flows

As well as a geological map of Ceres, we also have a picture of Ceres’ global geomorphology (its surface features). This shows that the surface of Ceres is peppered with impact craters, although the craters are not distributed evenly over the surface. Much more interesting are the three distinct types of mineral flow across the landscape, produced by the movement of ice-rich material, landslides or blankets of ejected particles following impact into ice-rich material. The distribution of the flow types varies with latitude – and the researchers think this means different surface layers of the asteroid contain different amounts of ice.

One of the most remarkable results is the detection of a sudden burst of highly energetic electrons over a period of around a week in June 2015, coinciding with a solar proton storm. The researchers think the protons fired out by the sun interacted with particles in Ceres’ weak atmosphere, creating a shock wave that accelerated the electrons. Based on observations by the Hubble Space Telescope, Ceres is believed to have a tenuous exosphere (outer atmosphere) of water vapour. The results from Dawn suggest that this may indeed be the case.

Together, this new set of information shows that Ceres is a world that has been shaped by a series of events, with a strong crust of magnesium- and ammonium-bearing phyllosilicates overlying an interior of briny ice and hydrated minerals. What other hidden secrets will be revealed as research continues on the trove of data from Ceres? Questions still remain about the variety of mineral deposits, the depth of the subsurface ice-rock layer, and, of course, the potential for organic material on the minor planet. The harvest from Ceres so far has been rich and promises to keep us busy for years to come.

The ConversationMonica Grady, Professor of Planetary and Space Sciences, The Open University

This article was originally published on The Conversation. Read the original article.

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Juno Reveals Jupiter’s Strange & Unique North Pole

A news release on reveals that NASA’s Juno spacecraft has sent back the first-ever images of Jupiter’s north pole, taken during the spacecraft’s first flyby of the planet with its instruments switched on. The images show storm systems and weather activity unlike anything previously seen on any of our solar system’s gas-giant planets.

As NASA's Juno spacecraft closed in on Jupiter for its Aug. 27, 2016 pass, its view grew sharper and fine details in the north polar region became increasingly visible, shown in this image captured by the JunoCam instrument. Credit: NASA/JPL-Caltech/SwRI/MSSS. Click/Tap for larger image.
As NASA’s Juno spacecraft closed in on Jupiter for its Aug. 27, 2016 pass, its view grew sharper and fine details in the north polar region became increasingly visible, shown in this image captured by the JunoCam instrument. Credit: NASA/JPL-Caltech/SwRI/MSSS. Click/Tap for larger image.

Juno successfully executed the first of 36 orbital flybys on Aug. 27 when the spacecraft came about 2,500 miles (4,200 kilometers) above Jupiter’s swirling clouds. The download of six megabytes of data collected during the six-hour transit, from above Jupiter’s north pole to below its south pole, took one-and-a-half days. While analysis of this first data collection is ongoing, some unique discoveries have already made themselves visible.

“First glimpse of Jupiter’s north pole, and it looks like nothing we have seen or imagined before,” said Scott Bolton, principal investigator of Juno from the Southwest Research Institute in San Antonio. “It’s bluer in color up there than other parts of the planet, and there are a lot of storms. There is no sign of the latitudinal bands or zone and belts that we are used to — this image is hardly recognizable as Jupiter. We’re seeing signs that the clouds have shadows, possibly indicating that the clouds are at a higher altitude than other features.”

Storm systems and weather activity unlike anything encountered in the solar system are on view in these color images of Jupiter's north polar region from NASA's Juno spacecraft.  Credit: NASA/JPL-Caltech/SwRI/MSSS. Click/Tap for larger image.
Storm systems and weather activity unlike anything encountered in the solar system are on view in these color images of Jupiter’s north polar region from NASA’s Juno spacecraft.
Credit: NASA/JPL-Caltech/SwRI/MSSS.
Click/Tap for larger image.

One of the most notable findings of these first-ever pictures of Jupiter’s north and south poles is something that the JunoCam imager did not see.

“Saturn has a hexagon at the north pole,” said Bolton. “There is nothing on Jupiter that anywhere near resembles that. The largest planet in our solar system is truly unique. We have 36 more flybys to study just how unique it really is.”

Along with JunoCam snapping pictures during the flyby, all eight of Juno’s science instruments were energized and collecting data. The Jovian Infrared Auroral Mapper (JIRAM), supplied by the Italian Space Agency, acquired some remarkable images of Jupiter at its north and south polar regions in infrared wavelengths.

The planet's southern aurora can hardly be seen from Earth due to our home planet's position in respect to Jupiter's south pole. Juno's unique polar orbit provides the first opportunity to observe this region of the gas-giant planet in detail. This image was acquired by Juno's Jovian Infrared Auroral Mapper (JIRAM) camera.  Credit: NASA/JPL Click/Tap for larger image.
The planet’s southern aurora can hardly be seen from Earth due to our home planet’s position in respect to Jupiter’s south pole. Juno’s unique polar orbit provides the first opportunity to observe this region of the gas-giant planet in detail. This image was acquired by Juno’s Jovian Infrared Auroral Mapper (JIRAM) camera.
Credit: NASA/JPL
Click/Tap for larger image.

“JIRAM is getting under Jupiter’s skin, giving us our first infrared close-ups of the planet,” said Alberto Adriani, JIRAM co-investigator from Istituto di Astrofisica e Planetologia Spaziali, Rome. “These first infrared views of Jupiter’s north and south poles are revealing warm and hot spots that have never been seen before. And while we knew that the first-ever infrared views of Jupiter’s south pole could reveal the planet’s southern aurora, we were amazed to see it for the first time. No other instruments, both from Earth or space, have been able to see the southern aurora. Now, with JIRAM, we see that it appears to be very bright and well-structured. The high level of detail in the images will tell us more about the aurora’s morphology and dynamics.”

Among the more unique data sets collected by Juno during its first scientific sweep by Jupiter was that acquired by the mission’s Radio/Plasma Wave Experiment (Waves), which recorded ghostly-sounding transmissions emanating from above the planet. These radio emissions from Jupiter have been known about since the 1950s but had never been analyzed from such a close vantage point.

“Jupiter is talking to us in a way only gas-giant worlds can,” said Bill Kurth, co-investigator for the Waves instrument from the University of Iowa, Iowa City. “Waves detected the signature emissions of the energetic particles that generate the massive auroras which encircle Jupiter’s north pole. These emissions are the strongest in the solar system. Now we are going to try to figure out where the electrons come from that are generating them.”

The Juno spacecraft launched on Aug. 5, 2011, from Cape Canaveral, Florida and arrived at Jupiter on July 4, 2016.

Source: News release and other articles on, used under public domain rights and in accordance with NASA’s Media Guidelines.

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Lift-off for NASA mission to collect grains from an asteroid that may be on collision course with Earth

By Monica Grady, The Open University.

It’s been a great few weeks for missions to small, primitive bodies. We’ve just about digested the latest news from the Ceres asteroid and rejoiced at the recovery of the comet-lander Philae, in time to wish a safe journey to NASA’s exciting new mission to Asteroid 101955 Bennu. OSIRIS-REx (short for Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorers – which is a bit of a mouthful) launched from Florida’s Cape Canaveral at 7:05pm EDT on September 8.

This is a very special mission – it’s not just going to map the composition of the asteroid, the mission is going to bring some of it back for us to study close up. The analysis of the precious grains may come in handy, as asteroid 101955 Bennu is on a collision course with Earth.

That last sentence is maybe a tad of an exaggeration – according to Dante Lauretta, the head of the mission, Bennu has around a 1 in 3,000 or so chance of colliding with Earth in the late 22nd century. Although such odds may seem quite frighteningly probable, and Bennu is high up on NASA’s table of potentially hazardous objects, the first possible collision with Earth is not until September 2175. By that time, I’m sure we will have learnt so much about the asteroid from the material brought back by OSIRIS-Rex that we will know how to deal with it.

There were three reasons why Bennu was selected as the target for OSIRIS-Rex: its orbital dynamics, its composition and its hazard potential. The orbital dynamics of Bennu are important because they will allow the spacecraft to get there in a reasonable timescale (estimated arrival date is August 2018) without requiring too much in the way of planetary swing-bys for gravitational assistance (it will make one Earth fly-by in September 2017). Bennu’s composition is also interesting – it has been determined by instruments on ground-based telescopes to be rich in carbon, one of the most primitive of asteroid types. So Bennu might be almost unchanged since the solar system formed some 4.6 billion years ago, and may contain a variety of organic compounds that became the building blocks of life.

The United Launch Alliance Atlas V rocket is ready for launch.

We have learned a huge amount about asteroids and comets from the Dawn and Rosetta missions – but both these missions have left many unanswered questions. It is quite frustrating to see some of the results and realise that the image resolution is just not quite sufficient to make out certain features. One of the first acts of a geologist, when examining rocks in the field, is to break open a sample, and look at the fresh surfaces of the interior material. Such an act is not an option on a mission that relies on remote sensing to identify different materials. But OSIRIS-Rex will make that possible when it returns the sample in 2023.

Sampling challenges

OSIRIS-Rex is not the first asteroid sample return mission: the Japanese Hayabusa mission brought back several hundred grains from Asteroid 25143 Itokawa in late 2010. The grains came from a stony asteroid, not a carbon-rich body, and do not seem to contain much in the way of organic material. And although NASA’s Stardust mission collected dust from the coma of comet Wild 2 in 2004, returning it to Earth in 2006, it has been very difficult to measure any organic compounds present in the dust because of the way the dust was collected (impact into aerogel).

But the sampling mechanism on-board OSIRIS-Rex is different: it is called the TAGSAM (for Touch-And-Go Sample Acquisition Mechanism). The TAGSAM is deployed at the end of an articulated arm and, when it touches the surface, a burst of nitrogen gas will fire down into the regolith. This will force material backwards and up into the TAGSAM. It is hoped that almost 100g of material with a variety of grain sizes will be collected for return to Earth. Analysis of the sample will be carried out by an international team of scientists; measurements will cover all aspects of the material’s composition and structure, especially the organic and water contents of the soil.

One experiment that OSIRIS-Rex will carry out as it orbits Bennu is to determine the extent of the so-called “Yarkovsky effect” on Bennu’s rotation. This effect is a force that acts on a rotating body in space, caused by the uneven release of heat from the surface of the asteroid. Once this is known, it will be possible to investigate whether we could use this force to change the orbit of Bennu.

For example, this could be achieved by focusing solar radiation onto its surface, which would change the strength of the Yarkovsky effect and ever so slightly alter Bennu’s course. Because the effect is so tiny, and difficult to measure precisely from Earth, the observations taken at Bennu will be the most accurate that have ever been made. This will allow engineers to calculate whether deflecting an asteroid using solar radiation is a realistic possibility, and the length of time it would take to shift an asteroid’s orbit from “collision course” to “missed by a mile”.

I have every faith that such calculations will be carried out before we get an even closer look at Bennu than we desire.

The ConversationMonica Grady, Professor of Planetary and Space Sciences, The Open University

This article was originally published on The Conversation. Read the original article.

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NASA’s Juno to Make Closest Pass to Jupiter

This dual view of Jupiter was taken on August 23, when NASA’s Juno spacecraft was 2.8 million miles (4.4 million kilometers) from the gas giant planet on the inbound leg of its initial 53.5-day capture orbit. Credits: NASA/JPL-Caltech/SwRI/MSSS
This dual view of Jupiter was taken on August 23, when NASA’s Juno spacecraft was 2.8 million miles (4.4 million kilometers) from the gas giant planet on the inbound leg of its initial 53.5-day capture orbit.
Credits: NASA/JPL-Caltech/SwRI/MSSS

This Saturday at 5:51 a.m. PDT, (8:51 a.m. EDT, 12:51 UTC) NASA’s Juno spacecraft will get closer to the cloud tops of Jupiter than at any other time during its prime mission. At the moment of closest approach, Juno will be about 2,500 miles (4,200 kilometers) above Jupiter’s swirling clouds and traveling at 130,000 mph (208,000 kilometers per hour) with respect to the planet. There are 35 more close flybys of Jupiter scheduled during its prime mission (scheduled to end in February of 2018). The Aug. 27 flyby will be the first time Juno will have its entire suite of science instruments activated and looking at the giant planet as the spacecraft zooms past.

“This is the first time we will be close to Jupiter since we entered orbit on July 4,” said Scott Bolton, principal investigator of Juno from the Southwest Research Institute in San Antonio. “Back then we turned all our instruments off to focus on the rocket burn to get Juno into orbit around Jupiter. Since then, we have checked Juno from stem to stern and back again. We still have more testing to do, but we are confident that everything is working great, so for this upcoming flyby Juno’s eyes and ears, our science instruments, will all be open.”

“This is our first opportunity to really take a close-up look at the king of our solar system and begin to figure out how he works,” Bolton said.

While the science data from the pass should be downlinked to Earth within days, interpretation and first results are not expected for some time.

“No other spacecraft has ever orbited Jupiter this closely, or over the poles in this fashion,” said Steve Levin, Juno project scientist from NASA’s Jet Propulsion Laboratory in Pasadena, California. “This is our first opportunity and there are bound to be surprises. We need to take our time to make sure our conclusions are correct.”

Not only will Juno’s suite of eight science instruments be on, the spacecraft’s visible light imager — JunoCam will also be snapping some closeups. A handful of JunoCam images, including the highest resolution imagery of the Jovian atmosphere and the first glimpse of Jupiter’s north and south poles, are expected to be released during the later part of next week.

Source: News release on republished under public domain rights and in accordance with the NASA media guidelines.

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Traveling to Mars with immortal plasma rockets

By Gary Li, University of California, Los Angeles.

Nearly 50 years after landing on the moon, mankind has now set its sights on sending the first humans to Mars. The moon trip took three days; a Mars trip will likely take most of a year. The difference is in more than just time.

We’ll need many more supplies for the trip itself, and when we get to the Red Planet, we’re going to need to set up camp and stay for a while. Carrying all this material will require a revolutionary rocket technology.

Saturn V rocket drawn to scale with Statue of Liberty. Apollo spacecraft and the moon are not to scale.

The Saturn V was the largest rocket ever built. It consumed an enormous amount of fuel in explosive chemical reactions that propelled the Apollo spacecraft into orbit. After reaching orbit, Apollo ejected the empty fuel tanks and turned on its own chemical rockets that used even more fuel to get to the moon. It took nearly a million gallons of various fuels just to send a few people on a day trip to our nearest extraterrestrial body.

So how could we send a settlement to Mars, which is more than 100 times farther away than the moon? The Saturn-Apollo combination could deliver only the mass equivalent of one railroad boxcar to the moon; it would take dozens of those rockets just to build a small house on Mars. Sadly, there are no alternatives for the “chemical” launch rocket; only powerful chemical explosions can provide enough force to overcome Earth’s gravity. But once in space, a new fuel-efficient rocket technology can take over: plasma rockets.

Gary Li’s University of California Grad Slam 2016 talk about his research.

The ‘electric vehicles’ of space

Plasma rockets are a modern technology that transforms fuel into a hot soup of electrically charged particles, known as plasma, and ejects it to push a spacecraft. Using plasma rockets instead of the traditional chemical rockets can reduce total in-space fuel usage by 90 percent. That means we could deliver 10 times the amount of cargo using the same fuel mass. NASA mission planners are already looking into using plasma rocket transport vehicles for ferrying cargo between Earth and Mars.

6 kW Hall Thruster. NASA JPL

The main downside to plasma rockets is their low thrust. Thrust is a measure of how strong a “push” the rocket can supply to the spacecraft. The most powerful plasma rocket flown in space, called a Hall thruster, would produce only enough thrust to lift a piece of paper against Earth’s gravity. Believe it or not, a Hall thruster would take many years of continuous pushing to reach Mars.

But don’t worry, weak thrust is not a deal breaker. Thanks to its revolutionary fuel efficiency, plasma rockets have enabled NASA to perform missions that would otherwise not be possible with chemical rockets. Just recently, the Dawn mission demonstrated the potential of plasma rockets by becoming the first spacecraft to orbit two different extraterrestrial bodies.

While the future of plasma rockets is bright, the technology still has unsolved problems. For example, what’s going to happen to a thruster that runs for the many years it takes to perform round-trip cargo missions to Mars? Most likely, it’ll break.

That’s where my research comes in. I need to find out how to make plasma rockets immortal.

Understanding plasma rockets

Model plasma rocket diagram. Most similar to an ion thruster design. Author provided,  CC BY-ND

To do this, we need to understand how a plasma rocket works. The rocket creates a plasma by injecting electrical energy into a gaseous fuel, stripping negatively charged electrons from the positively charged ions. The ions are then shot out the back of the rocket, pushing the spacecraft forward.

Unfortunately, all that energy in plasma does more than propel spaceships – it wants to destroy any material it comes into contact with. Electric forces from the negatively charged walls cause the ions to slam into the wall at very high speeds. These collisions break atoms off the wall, slowly weakening it over time. Eventually, enough ions hit the wall that the entire wall breaks, the thruster stops functioning and your spacecraft is now stuck in space.

It’s not enough to use tougher materials to withstand the bombardment: There will always be some amount of damage regardless of how strong the material is. We need a clever way of manipulating the plasma, and the wall material, to avoid damage.

A self-healing wall

Wouldn’t it be great if the chamber wall could repair itself? It turns out there are two physical effects that can allow this to happen.

Illustration of three possible scenarios for a wall atom that comes off: 1) it’s lost forever, 2) it intercepts a wall and deposits or 3) it becomes ionized and is accelerated by electric forces to deposit on the wall.

The first is known as ballistic deposition and is present in materials with microscopic surface variations, like spikes or columns. When an ion hits the wall, a piece of these microfeatures that breaks off can fly in any direction. Some of these pieces will hit nearby protruding parts of the surface and stick, leaving the wall effectively undamaged. However, there will always be atoms that fly away from the wall and are lost forever.

Microstructures on a material sample viewed under a Scanning Electron Microscope. Chris Matthes (UCLA),  CC BY-ND

The second phenomenon is less intuitive and depends on the plasma conditions. Imagine the same scenario where the wall particle breaks off and flies into the plasma. However, instead of being lost forever, the particle suddenly turns around and goes straight back to the wall.

This is similar to how a baseball tossed straight up into the air turns around and drops back to your hand. With the baseball, gravity stops the ball from going up any higher and pulls it back down to the ground. In a thruster, it’s the electric force between the negatively charged wall and the wall particle itself. It comes off neutrally charged, but can lose its electron in the plasma, becoming positively charged. The result is that the particle is pulled back toward the wall, in a phenomenon known as plasma redeposition. This process can be controlled by changing the density and temperature of the plasma.

Testing different materials

Sample materials being assessed in the UCLA Plasma-interactions test facility.

Here at UCLA, I create a plasma and smash it into microfeatured materials, to measure the effects of ballistic deposition and plasma redeposition. Remember, ballistic deposition depends on the wall’s surface structures, while plasma redeposition depends on the plasma. For my initial study, I adjusted the plasma conditions so there was no plasma redeposition, and only ballistic deposition occurred.

Then I turned my attention from the plasma to the wall. The first microfeatured sample I tested had its damage reduced by 20 percent. By improving the design of the microfeatures, the damage can be reduced even further, potentially as much as 50 percent. Such a material on a thruster could make the difference between getting to Mars and getting stuck halfway. The next step is to include the effects of plasma redeposition and to determine whether a truly immortal wall can be achieved.

As plasma thrusters become ever more powerful, they become more able to damage their own walls, too. That increases the importance of a self-healing wall. My ultimate goal is to design a thruster using advanced materials that can last 10 times as long as any Mars mission requirement, making it effectively immortal. An immortal wall would solve this problem of thruster failure, and allow us to ferry the cargo we need to begin building mankind’s first outpost on Mars.

The ConversationGary Li, Ph.D. Candidate in Mechanical and Aerospace Engineering, University of California, Los Angeles

This article was originally published on The Conversation. Read the original article.

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Imagine Landing On Pluto [Video]

Imagine a future spacecraft following New Horizons’ trailblazing path to Pluto, but instead of flying past its target, the next visitor touches down in the midst of tall mountains on the icy plains of Pluto’s heart.

There’s no need to wait for that fantasy trip, thanks to new video produced by New Horizons scientists. Made from more than 100 New Horizons images taken over six weeks of approach and close flyby, the video offers a “trip” to Pluto. It starts with a distant spacecraft’s view of Pluto and its largest moon, Charon – closing the distance day by day – with a dramatic “landing” on the shoreline of Pluto’s frozen plains.

“Just over a year ago, Pluto was just a dot in the distance,” said New Horizons Principal Investigator Alan Stern, of the Southwest Research Institute, Boulder, Colorado. “This video shows what it would be like to ride aboard an approaching spacecraft and see Pluto grow to become a world, and then to swoop down over its spectacular terrains as if we were approaching some future landing.”


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Juno Sends First Images to Earth Post-Entry into Orbit

This color view from NASA's Juno spacecraft is made from some of the first images taken by JunoCam after the spacecraft entered orbit around Jupiter on July 5th (UTC). Credits: NASA/JPL-Caltech/SwRI/MSSS. Click/Tap for larger image.
This color view from NASA’s Juno spacecraft is made from some of the first images taken by JunoCam after the spacecraft entered orbit around Jupiter on July 5th (UTC).
Credits: NASA/JPL-Caltech/SwRI/MSSS. Click/Tap for larger image.

The JunoCam camera aboard NASA’s Juno mission is operational and sending down data after the spacecraft’s July 4 arrival at Jupiter. Juno’s visible-light camera was turned on six days after Juno fired its main engine and placed itself into orbit around the largest planetary inhabitant of our solar system. The first high-resolution images of the gas giant Jupiter are still a few weeks away.

“This scene from JunoCam indicates it survived its first pass through Jupiter’s extreme radiation environment without any degradation and is ready to take on Jupiter,” said Scott Bolton, principal investigator from the Southwest Research Institute in San Antonio. “We can’t wait to see the first view of Jupiter’s poles.”

The new view was obtained on July 10, 2016, at 10:30 a.m. PDT (1:30 p.m. EDT, 5:30 UTC), when the spacecraft was 2.7 million miles (4.3 million kilometers) from Jupiter on the outbound leg of its initial 53.5-day capture orbit.  The color image shows atmospheric features on Jupiter, including the famous Great Red Spot, and three of the massive planet’s four largest moons — Io, Europa and Ganymede, from left to right in the image.

“JunoCam will continue to take images as we go around in this first orbit,” said Candy Hansen, Juno co-investigator from the Planetary Science Institute, Tucson, Arizona. “The first high-resolution images of the planet will be taken on August 27 when Juno makes its next close pass to Jupiter.”

JunoCam is a color, visible-light camera designed to capture remarkable pictures of Jupiter’s poles and cloud tops. As Juno’s eyes, it will provide a wide view, helping to provide context for the spacecraft’s other instruments. JunoCam was included on the spacecraft specifically for purposes of public engagement; although its images will be helpful to the science team, it is not considered one of the mission’s science instruments.

The Juno team is currently working to place all images taken by JunoCam on the mission’s website, where the public can access them.

During its mission of exploration, Juno will circle the Jovian world 37 times, soaring low over the planet’s cloud tops — as close as about 2,600 miles (4,100 kilometers). During these flybys, Juno will probe beneath the obscuring cloud cover of Jupiter and study its auroras to learn more about the planet’s origins, structure, atmosphere and magnetosphere.

Source: Press release from republished under public domain rights and in compliance with the NASA Media Usage Guidelines.

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