Posted on by Jason Major

Enceladus On Display In Newest Images From Cassini

Enceladus' southern ice geysers are brilliant in backlit sunlight (NASA/JPL/SSI/J. Major)

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The latest images are in from Saturn’s very own personal paparazzi, NASA’s Cassini spacecraft, fresh from its early morning flyby of the ice-spewing moon Enceladus. And, being its last closeup for the next three years, the little moon didn’t disappoint!

The image above is a composite I made from two raw images (this one and this one) assembled to show Enceladus in its crescent-lit entirety with jets in full force. The images were rotated to orient the moon’s southern pole — where the jets originate — toward the bottom.

Cassini was between 72,090 miles (116,000 km) and 90,000 miles (140,000 km) from Enceladus when these images were acquired.

This morning’s E-19 flyby completed a trio of recent close passes by Cassini of the 318-mile (511-km) -wide moon, bringing the spacecraft as low as 46 miles (74 km) above its frozen surface. The goal of the maneuver was to gather data about Enceladus’ internal mass — particularly in the region around its southern pole, where a reservoir of liquid water is thought to reside — and also to look for “hot spots” on its surface that would give more information about its overall energy distribution.

Cassini had previously discovered that Enceladus radiates a surprising amount of heat from its surface, mostly along the “tiger stripe” features — long, deep furrows (sulcae) that gouge its southern hemisphere, they are the source of the water-ice geysers.

Cassini also used the flyby opportunity to study Enceladus’ gravitational field.

By imaging the moon with backlit lighting from the Sun the highly-reflective ice particles in the jets become visible. More direct lighting reduces the jets’ visibility in images, which must be exposed for the natural light of the scene or risk “blowing out” due to Enceladus’ natural high reflectivity.

The images below are raw spacecraft downloads right from the Cassini’s imaging headquarters in Boulder, CO.

Enceladus' geysers in action on May 2, 2012. (NASA/JPL/SSI)
Enceladus sprays ice into the hazy E ring, which orbits Saturn (NASA/JPL/SSI)

Cassini also swung closely by Dione during this morning’s flyby but the images from that encounter aren’t available yet. Stay tuned to Universe Today for more postcards from Saturn!

As always, you can follow along with the ongoing Cassini mission on JPL’s dedicated site here, as well as on the Cassini Imaging Central Laboratory for Operations (CICLOPS) site.

Posted on by Jason Major

ESA Turns On The JUICE For New Jupiter Mission

Galileo image of Ganymede, Jupiter's - and the Solar System's - largest moon. (Ted Stryk)

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The European Space Agency has given the go-ahead for an exciting mission to explore the icy moons of Jupiter, as well as the giant planet itself.

JUICE — JUpiter ICy moons Explorer — will consist of a solar-powered spacecraft that will spend 3.5 years within the Jovian system, investigating Ganymede, Europa and the upper atmosphere of Jupiter. Anticipated to launch in June 2022, JUICE would arrive at Jupiter in early 2030.

As its name implies, JUICE’s main targets are Jupiter’s largest icy moons — Ganymede and Europa — which are thought to have liquid oceans concealed beneath their frozen surfaces.

The largest moon in the Solar System, Ganymede is also thought to have a molten iron core generating a magnetic field much like Earth’s. The internal heat from this core may help keep Ganymede’s underground ocean liquid, but the dynamics of how it all works are not quite understood.

JUICE will also study the ice-coated Europa, whose cueball-smooth surface lined with cracks and jumbled mounds of frozen material seem to be sure indicators of a subsurface ocean, although how deep and how extensive is might be are still unknown — not to mention its composition and whether or not it could be hospitable to life.

The rust-colored cracks lining Europa's otherwise smooth surface hint at a subsurface ocean. (Ted Stryk)

“JUICE will give us better insight into how gas giants and their orbiting worlds form, and their potential for hosting life,” said Professor Alvaro Giménez Cañete, ESA’s Director of Science and Robotic Exploration.

The JUICE spacecraft was originally supposed to join a NASA mission dedicated to the investigation of Europa, but NASA deemed their proposed mission too costly and it was cancelled. According to Robert Pappalardo, study scientist for the Europa mission based at JPL, NASA may still supply some instruments for the spacecraft “assuming that the funding situation in the United States can bear it.”

Artist's rendering of JUICE at Jupiter. (ESA/AOES)

JUICE will also capture images of Jupiter’s moon Callisto and search for aurorae in the gas giant’s upper atmosphere, as well as measure the planet’s powerful magnetic field. Once arriving in 2030, it will spend at least three years exploring the Jovian worlds.

Read more in today’s news release from Nature, and stay tuned to ESA’s JUICE mission page here.

Recalibrated Galileo images © Ted Stryk. See more of Ted’s excellent work on his site Planetary Images From Then And Now.

Posted on by Jason Major

OMG Space

OMG Space attempts to portray the scale sizes and distances in the Solar System

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“You may think it’s a long way down the road to the chemist’s, but that’s just peanuts to space.” – Douglas Adams

Standard classroom models and textbook illustrations of the Solar System, regardless of how pretty they are, all share one thing in common: they’re wrong. Ok, maybe not wrong, but definitely inaccurate… especially in regards to scale. And understandably so, as it’s nearly impossible to portray in a convenient manner the sheer amount of space there is between the planets and their relative sizes. Even if a model manages to show one or the other in a straightforward, linear fashion, it usually doesn’t show both.

This one does.

OMG Space is a web page made by Margot Trudell as graphic design thesis project at Toronto’s OCAD University. Displayed on the Visual.ly portfolio site, Margot’s expansive infographic shows the Sun, planets and some minor bodies to scale, both in terms of relative size and distance. By clicking on a planet’s name at the bottom of the page you’ll be whisked away toward it, giving a sense of how very far it really is between the many worlds that make up our own little Solar System.

And if that’s not enough, Margot has included a descriptive chart for each world that gives basic information on distance from the Sun, orbital period and moon count as well as details on visiting exploration missions — past, present and planned. These can be accessed by clicking on the respective worlds once you arrive.

Each planet has an infographic associated with it, showing physical characteristics and exploration timelines. (M. Trudell)

“I created the infographics first and as I worked on them decided they needed more context, and the idea of creating a to scale version of our solar system came to mind,” Margot told Universe Today. “The project was initially intended to be all print, but knowing the real scale of our solar system I eventually came up with the idea of using the infiniteness of the web to my advantage.”

If you watch the scroll bar on the right side of the page (and I do suggest resizing the page to fill your screen as much as possible) you’ll also get a sense of how much space you’re traversing as you zip between worlds. And that’s just taking into consideration the average distances between each planet at opposition. In reality, they’re never lined up in a row like that!

If you’re so inclined you can also scroll up and down manually… if only to see how long it takes you to not get anywhere.

“My favourite thing to do on OMG Space’s website is go to Earth and then click on the link to the Moon,” Margot said. “The small distance you move yet the big gap you see… it gives you a whole new perspective on how far people traveled to get to the moon and back, and it shows how far the moon really is from Earth (I feel that it’s always portrayed as being almost right beside us) and makes you consider how powerful those rockets must have been to get us that far.

“It gives you a bit of that ‘OMG’ feeling that the project is named for.”

Yes, OMG indeed.

Infographics by Margot Trudell. See more of Margot’s work here.

Posted on by Jason Major

Cassini Exposes Phoebe As More Planet Than Moon

Color-composite image of Phoebe as seen by Cassini in 2009.

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Saturn’s curious moon Phoebe features a heavily-cratered shape and orbits the ringed planet backwards at a considerable distance of over 8 million miles (12.8 million km). According to recent news from the Cassini mission Phoebe may actually be a Kuiper Belt object, having more in common with planets than it does with any of Saturn’s other satellites.

132 miles (212 km) in diameter, Phoebe is the largest of Saturn’s irregular moons — a cloud of small, rocky worlds held in distant orbits at highly inclined paths. Its backwards (retrograde) motion around Saturn and dense composition are dead giveaways that it didn’t form in situ within the Saturnian system, but rather was captured at some point when it strayed too close to the gas giant.

In fact it’s now thought that Phoebe may be a remnant from the formation of the Solar System — a planetesimal — with its own unique history predating its adoption into Saturn’s extended family of moons.

“Unlike primitive bodies such as comets, Phoebe appears to have actively evolved for a time before it stalled out,” said Julie Castillo-Rogez, a planetary scientist at NASA’s Jet Propulsion Laboratory. “Objects like Phoebe are thought to have condensed very quickly. Hence, they represent building blocks of planets. They give scientists clues about what conditions were like around the time of the birth of planets and their moons.”

Although Phoebe is heavily eroded and irregularly-shaped today at one time it may have been much rounder. But an early composition of radioactive elements would have generated heat, and as it warmed it “deflated” through compression, growing denser and denser.

Map of Phoebe's surface. (NASA/JPL-Caltech/SSI/Cornel)

Now, Phoebe exhibits a similar density to Pluto — another denizen of the Kuiper Belt.

At some point Phoebe may even have had water, kept liquid by its radioactive heat. That is, until the heat faded and it froze, creating the icy surface detected by Cassini’s instruments.

Still, Cassini’s study of Saturn’s moons has provided scientists with clues to what was happening much earlier on in the Solar System. What caused Phoebe to drift inwards to be caught up in orbit around Saturn? How did it survive such a supposed shuffling of planets and other worlds did not? As Cassini continues its investigation answers — and undoubtedly even more questions — will be uncovered.

Read more on NASA’s news release here.

Image: NASA/JPL/SSI. Color composition by Gordan Ugarkovic.

Posted on by Jason Major

MESSENGER Reveals Mercury’s Colors

MESSENGER image of Mercury, acquired with its Wide Angle Camera on March 21, 2012.

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The subtle yet surprisingly varied colors of Mercury are revealed in the latest images from NASA’s MESSENGER spacecraft, now in its extended mission and second year in orbit.

The image above, a composite of Wide Angle Camera images acquired in 996, 748 and 433 nanometers for red, green and blue, shows a semi-lit limb of Mercury with the bright rayed crater Debussy visible at left. (The image has been rotated 180 degrees from the original, and color saturation was boosted by 25%.)

Named for the French composer Claude Debussy of “Claire de Lune” fame, the crater itself is approximately 50 miles (80 km) wide. It was first detected by ground-based radar telescopes in 1969 as a bright spot.

Now, 43 years later, we have a spacecraft in orbit sending back images like this. Amazing.

The various colors seen across Mercury are due to different mineral compositions of the geologic regions. The exact compositions are not yet known, and the current puzzle that researchers are trying to solve with MESSENGER is to figure out what materials make up Mercury’s complex, multi-hued surface. That will also give a clue as to what’s inside the planet and how it evolved… as well as how it is currently evolving today.

(Read about some surprising discoveries regarding Mercury’s interior.)

The image below is from MESSENGER’s Visual and Infrared Spectrograph (VIRS) and shows a map of Mercury’s surface, with RGB colors corresponding to different mineralogical compositions.

Sinusoidal equal area projection map of Mercury from MESSENGER's VIRS instrument.

Younger surface materials that are brighter at visible wavelengths and less affected by space weathering show up in reds, yellows and greens. Materials that may have relatively higher iron contents show up in blue.

These are Mercury’s “other colors”… maybe not what we would see with our own eyes, but beautiful nonetheless to planetary scientists!

See the above image on the MESSENGER website here.

Image credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

Posted on by Jason Major

The Case of the Missing Dark Matter

Artist's impression of dark matter surrounding the Milky Way. (ESO/L. Calçada)

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A survey of the galactic region around our solar system by the European Southern Observatory (ESO) has turned up a surprising lack of dark matter, making its alleged existence even more of a mystery.

The 2.2m MPG-ESO telescope, used in the survey. (ESO/H.H.Heyer)

Dark matter is an invisible substance that is suspected to exist in large quantity around galaxies, lending mass but emitting no radiation. The only evidence for it comes from its gravitational effect on the material around it… up to now, dark matter itself has not been directly detected. Regardless, it has been estimated to make up 80% of all the mass in the Universe.

A team of astronomers at ESO’s La Silla Observatory in Chile has mapped the region around over 400 stars near the Sun, some of which were over 13,000 light-years distant. What they found was a quantity of material that coincided with what was observable: stars, gas, and dust… but no dark matter.

“The amount of mass that we derive matches very well with what we see — stars, dust and gas — in the region around the Sun,” said team leader Christian Moni Bidin of the Universidad de Concepción in Chile. “But this leaves no room for the extra material — dark matter — that we were expecting. Our calculations show that it should have shown up very clearly in our measurements. But it was just not there!”

Based on the team’s results, the dark matter halos thought to envelop galaxies would have to have “unusual” shapes — making their actual existence highly improbable.

Still, something is causing matter and radiation in the Universe to behave in a way that belies its visible mass. If it’s not dark matter, then what is it?

“Despite the new results, the Milky Way certainly rotates much faster than the visible matter alone can account for,” Bidin said. “So, if dark matter is not present where we expected it, a new solution for the missing mass problem must be found.

“Our results contradict the currently accepted models. The mystery of dark matter has just became even more mysterious.”

Read the release on the ESO site here.

Posted on by Jason Major

Cassini Slips Through Enceladus’ Spray

Cassini's latest view of Enceladus' icy spray, acquired on April 14, 2012.

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Spray it again, Enceladus! This Saturday the Cassini spacecraft paid another visit to Enceladus, Saturn’s 318-mile-wide moon that’s become famous for its icy geysers.During its latest close pass Cassini got a chance to “taste” Enceladus’ spray using its ion and neutral mass spectrometer, giving researchers more information on what sort of watery environment may be hiding under its frozen, wrinkled surface.

The image above shows a diagonal view of Enceladus as seen from the night side. (The moon’s south pole is aimed at a 45-degree angle to the upper right.) Only by imaging the moon backlit by the Sun can the geysers of fine, icy particles be so well seen.

During the flyby Cassini passed within 46 miles (74 km) of Enceladus’ surface.

This image was captured during the closest approach, revealing the distressed terrain of Enceladus’ south pole. Although a bit blurry due to the motion of the spacecraft, boulders can be made out resting along the tops of high , frozen ridges. (Edited from the original raw image to enhance detail.)

Enceladus' southern fissures, the source of its spray. (NASA/JPL/SSI/J. Major)

This flyby occurred less than three weeks after Cassini’s previous visit to Enceladus. Why pay so much attention to one little moon?

Basically, it’s the one place in our solar system that we know of where a world is spraying its “habitable zone” out into space for us to sample.

“More than 90 jets of all sizes near Enceladus’s south pole are spraying water vapor, icy particles, and organic compounds all over the place,” said Carolyn Porco, planetary scientist and Cassini Imaging science team leader, during a NASA interview in March. “Cassini has flown several times now through this spray and has tasted it. And we have found that aside from water and organic material, there is salt in the icy particles. The salinity is the same as that of Earth’s oceans.

“In the end, it’s the most promising place I know of for an astrobiology search,” said Porco. (Read the full interview here.)

A crescent-lit Enceladus sprays its "habitable zone" out into space.

Not to be left out, Tethys was also paid a visit by Cassini. The 662-mile-wide moon boasts one of the most extensively cratered surfaces in the Solar System, tied with its sister moons Rhea and Dione. In this raw image captured by Cassini on April 14, we can see some of the moon’s ancient, larger craters, including Melanthius with its enormous central peak.

Saturn's moon Tethys, imaged by Cassini on April 14, 2012.

Cassini passed Tethys at a distance of about 6,000 miles (9000 km) after departing Enceladus. Cassini’s composite infrared spectrometer looked for patterns in Tethys’ thermal signature while other instruments studied the moon’s geology.

Image credits: NASA/JPL/Space Science Institute. See more images from the Cassini mission on the CICLOPS site here.

 

Posted on by Jason Major

Hubble Reveals Curious Auroras on Uranus

Bright spots of Uranus' short-lived auroras have been imaged with the Hubble Space Telescope.

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Astronomers have finally succeeded in capturing the first Earth-based images of the curious and fleeting auroras of Uranus using the Hubble Space Telescope, careful planning… and no small amount of luck.

Unlike Earthly auroras, whose long-lived curtains of glowing green, red and purple have been the subject of countless stunning photos over the past months, Uranus’ auroras are relatively dim and short-lived, lasting only several minutes at most. They were first witnessed on Uranus by Voyager 2 in 1986, but never by any Earth-based telescopes until November of 2011. Using Hubble, an international team of astronomers led by Laurent Lamy from the Observatoire de Paris in Meudon, France spotted two instances of auroras on the distant planet… once on November 16 and again on the 29th.

Two instances of Uranian aurora imaged in Nov. 2011. (L. Lamy)

Auroras are known to be created by a planet’s magnetosphere, which on Earth is aligned closely with the rotational axis — which is why auroras are seen nearest the polar latitudes. But Uranus’ magnetic field is quite offset from its rotational axis, which in turn is tipped nearly 98 degrees relative to its orbital path. In other words, Uranus travels around the Sun rolling on its side! And with a 60-degree difference between its magnetic and rotational axis, nothing on Uranus seems to point quite where it should. This — along with its 2.5-billion-mile (4 billion km) distance — makes for a “very poorly known” magnetic field.

“This planet was only investigated in detail once, during the Voyager flyby, dating from 1986. Since then, we’ve had no opportunities to get new observations of this very unusual magnetosphere,” said Laurent Lamy, lead author of the team’s paper Earth-based detection of Uranus’ aurorae.

Rather than rings of bright emissions, as witnessed on Earth as well as Saturn and Jupiter, the Uranian auroras appeared as bright spots of activity on the planet’s daytime side — most likely a result of Uranus’ peculiar orientation, as well as its seasonal alignment.

It’s not yet known what may be happening on Uranus’ night side, which is out of view of Hubble.

When Voyager 2 passed by Uranus in 1986 the planet was tipped such that its rotational axis was aimed toward the Sun. This meant that its magnetic axis —  offset by 60 degrees — was angled enough to encounter the solar wind in much the same way that Earth’s does. This created nightside auroras similar to Earth’s that Voyager saw.

By 2011, however, Uranus — which has an 84-year-long orbit — was near equinox and as a result its magnetic axis was nearly perpendicular with its orbital plane, aiming each end directly into the solar wind once a day. This makes for very different kinds of auroras than what was seen by Voyager; in fact, there’s really nothing else like it that astronomers know of.

“This configuration is unique in the solar system,” said Lamy.

Further investigations of Uranus’ auroras and magnetic field can offer insight into the dynamics of Earth’s own magnetosphere and how it interacts with the solar wind, which in turn affects our increasingly technological society.

The team’s paper will be published Saturday in Geophysical Research Letters, a journal of the American Geophysical Union.

Read the release from the AGU here.

Posted on by Jason Major

Watch Mercury Get Smacked By CMEs

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The bright object in the center of this video sequence is the planet Mercury, seen by NASA’s STEREO-B spacecraft as it was pummeled by wave after wave of solar material ejected from the Sun during the week of March 25 – April 2, 2012.

The video above was released by NASA’s Goddard Space Flight Center earlier today. The Sun is located just off-frame to the left, while Earth would be millions of miles to the right.

Proof that it’s not easy being first rock from the Sun!

Video credit: NASA/GSFC/STEREO

Posted on by Jason Major

Ice Sculptures Fill The Deepest Parts of Mars

Credit: NASA/JPL/Arizona State University

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One of the “weirdest and least understood” areas of Mars, the enormous Hellas Impact Basin contains strange flowing landforms that bespeak of some specialized and large-scale geologic process having taken place. The HiRISE camera aboard NASA’s Mars Reconnaissance Orbiter recently captured the image above, showing what’s being called “lava lamp terrain” — stretched and contorted surface that looks like overworked modeling clay or pulled taffy… or, with a bit of imagination, the melted, mesmerizing contents of a party light from another era.

At 1,400 miles (2,300 km) across, Mars’ Hellas Basin is one of the largest impact craters in the entire Solar System. Its vast interior sinks to a depth of about 23,000 feet (7152 meters) below Mars’ average surface elevation (Martian “sea level”, if you will) and thus its floor is often shrouded by haze and dust, making visual imaging difficult.

The “lava lamp” terrain is just one of many different types of landforms that are found in the basin, although many of these banded features are found in the northwest area — which is also the deepest part of the basin. If there had been water in the region at some point in the planet’s history, it would have concentrated there.

Although the texture at first appears as if it could be volcanic in origin, it’s thought that flowing water or ice may actually be the source.

Researchers are currently working to determine how the Hellas Basin became so smoothly sculpted. Nicolas Thomas, Professor of Experimental Physics at the University of Bern, Switzerland, told Universe Today:

“There are a lot of very interesting images from this area and we are trying to get more data (including stereo) to understand better what’s going on and to try to establish what process is responsible for the numerous bizarre features we see. We are hoping to make some more progress in the next few months.”

Example of banded terrain. Compare the relatively fresh appearance of the bands with the older terrain seen to the left of this sub-image. (NASA/JPL/University of Arizona/N. Thomas et al.)

This hypothesis is also in line with the possibility of Hellas Basin having once been a giant lake.

“Together with the observations of isolated areas and the lack of obvious caldera(s), it is difficult to envisage a volcanic origin for these features and we currently tend towards a mechanism involving ice,” Thomas stated in an abstract of a presentation given at the Europlanet Conference in 2010.

Read the full abstract here, and see this and more high-resolution images from Mars on the HiRISE website.