Maelstrom’s Edge!

Cassini has given us this new close-up of the outer edge of the bizarre and beautiful hexagon-shaped jet stream system at Saturn’s north pole, along with many smaller storms. Maybe ‘small’ isn’t quite the right the word. For a sense of scale: the entire Earth would fit inside the hexagon.

See more from the Cassini mission to Saturn.

Find out more about Saturn itself.

Saturn's polar hexagon,

A close-up of the outer edge of Saturn’s polar hexagon, along with many smaller storms, taken on March 28, 2014 and received on Earth March 31. NASA / JPL / SSI / animation by Bill Dunford

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Dancing With Saturn

As I type this, the robotic spacecraft Cassini is traveling at 2.4 kilometers per second (about 5,300 MPH) relative to the planet Saturn. On April 9th, when Cassini makes its closest approach to the planet during this current orbit, the craft will reach nearly 9 kilometers per second (about 20,000 MPH). For all that amazing speed, the pictures we see from Cassini are usually still shots, arrestingly beautiful–but also arrested in time.

Fortunately, we can get a sense of Cassini’s intricate ongoing dance with Saturn and its moons, thanks to sequences of still images strung together into simple animations. Sometimes these sequences are just a series of routine observations; sometimes they are planned with moving images in mind. This magic is possible thanks to the Cassini engineering and science teams, who coordinate to build a list of painstakingly precise instructions, which they radio across a billion kilometers of space to the Saturn system. Cassini does the rest, spinning and pirouetting to orient its cameras just so, even as it careens at high speed past rings and icy moons.

The results are often striking. Here are a few of my favorites. I’ve applied very little post-processing to these sequences, but what they lack in polish compared to Hollywood CGI, they make up in being real.

Surging Sunlight

Surging Sunlight – The bright glint of an opposition surge seems to follow Cassini as it observes Saturn’s rings over the course of a couple of hours with the sun directly behind the spacecraft. NASA / JPL / SSI / Animation by Bill Dunford

Purple Haze in Motion

Purple Haze in Motion – As Cassini neared Saturn’s moon Titan for a close pass, layers of haze in the giant moon’s atmosphere revealed themselves. (The color in these images is added.) NASA / JPL / SSI / Animation by Bill Dunford

Ice Shepherd

Ice Shepherd – Cassini caught the shepherd moon Prometheus at work herding the icy particles of Saturn’s F ring with its gentle gravitational field. NASA / JPL / SSI / Animation by Bill Dunford

Buzzing Dione

Buzzing Dione – Cassini captured this series of images as it flew near the ice world Dione in 2005. NASA / JPL / SSI / Animation by Bill Dunford

Epimetheus and Family

Epimetheus and Family – Epimetheus, as tracked by Cassini over the course of almost an hour as the moonlet orbited in the ring plane, along with other members of Saturn’s family of worlds. NASA / JPL / SSI / Animation by Bill Dunford

Spinning Saturn

Spinning Saturn – Cassini watched over the span of about 90 minutes as Saturn turned on its axis, its atmosphere churned, and icy moons circled the scene. NASA / JPL / SSI / Animation by Bill Dunford

Enceladus Amid the Stars

Enceladus Amid the Stars – Saturn’s moon Enceladus, with its intriguing ice geysers, seems to be rocketing through space in this series of images taken by Cassini. NASA / JPL / SSI / Animation by Bill Dunford

Mimas and the Rings

Mimas and the Rings – Cassini tracks Saturn’s moon Mimas as it orbits near the rings. The sequence shown here took about 11 minutes to capture. NASA / JPL / SSI / Animation by Bill Dunford

And here’s one more that was previously uploaded to the Saturn section of the Bruce Murray Space Image Library. I have to sneak it in, just because I think it happens to be one of the most amazing sights in the history of all exploration.
Saturn’s north polar vortex (an animation)

Saturn's north polar vortex (an animation)

Saturn’s north polar vortex (an animation) – Cassini took 14 images of Saturn’s north polar vortex on November 27, 2012 over a period of many hours as the planet rotated beneath it. The 14 images have been processed to remove the geometric effects of Cassini’s oblique viewpoint and of Saturn’s rotation, holding the outer bright ring of white clouds fixed. With these motions removed, you can see individual vortices rotating and shearing, and the central clouds rotating faster than the outer ones. NASA / JPL / SSI / Kevin McAbee

This article originally appeared as a guest post on The Planetary Society site.


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Harrison “Jack” Schmitt was the last person to step down onto the Moon. He was also the only professional geologist to work on the lunar surface, which he did during the Apollo 17 expedition to the Taurus-Littrow Valley.

The Moon’s geology still fascinates Dr. Schmitt. Just last week, in fact, he spoke about his lunar fieldwork to scientists gathered at the 45th Lunar and Planetary Science Conference being held this week in Texas. He told his audience that the samples and field notes from the Apollo 17 mission are still useful today, but that’s not all–there’s another, newer tool available to Moon explorers: the Lunar Reconnaissance Orbiter. High-resolution images from the robotic spacecraft provide fresh perspectives from on high, such as revealing boulder tracks at the Apollo landing sites that astronauts didn’t see from the ground.

Schmitt left the Moon in 1972. No one has been back since. But thanks to the Lunar Reconnaissance Orbiter, you don’t have to be an astronaut to see lunar landscapes up close. LRO returns images with such great detail that objects as small as individual boulders, or even human-made objects like the lunar landers, are easy to spot.

My favorite LRO shots are taken at a highly oblique angle rather than looking straight down. Views like that, especially when the sun is low on the horizon, almost look like what you might see if you were standing there in person.

At the bottom of this page I’ve gathered a few of these postcards from the Moon. Each offers a nice perspective on the landscape, but to really feel like you’re getting your boots dirty at the locations they show, you’ll want to click on the small pictures in order to zoom in on the details that are only visible in the much larger versions.

For example, here’s a detail from the Hausen Crater image:

Hausen Crater Central Peaks, Detail

Hausen Crater Central Peaks, Detail – Who’s up for a hike? The central peaks in the Moon’s Hausen Crater, a detail from the much larger image below. Credit: NASA / GSFC / ASU

And here’s another example, this one from Giordano Bruno Crater:

Giordano Bruno Crater, Detail

Giordano Bruno Crater, Detail – Beware of sliding boulders! A detail from a larger image of the Moon’s Giordano Bruno Crater, as imaged by LRO. Credit: NASA / GSFC / ASU

Here are some more lunar locations. Clicking on each will lead to a page where you can enlarge the image and explore the full desolation in all its magnificence. All of these images were captured in the past couple of years, and most have not been widely published elsewhere. Happy moonwalking!

Anaxagoras Crater

Anaxagoras Crater – An oblique view into the Moon’s Anaxagoras Crater, as seen by the Lunar Reconnaissance Orbiter with the Sun low on the horizon. Anaxagoras has a diameter of about 51 km. NASA / GSFC / ASU

Giordano Bruno Crater

Giordano Bruno Crater – A view of Giordano Bruno, a 22-km-wide impact crater on the far side of the Moon. When viewed large, the high resolution and oblique angle of this Lunar Reconnaissance Orbiter image almost make it seem like you’re standing right on the edge of the crater. Credit: NASA / GSFC / ASU

Antoniadi Crater Central Peak

Antoniadi Crater Central Peak – The unusually smooth floor of Antoniadi Crater includes the lowest point on the Moon. The Lunar Reconnaissance Orbiter captured this oblique view of the peak at the center of the crater, which is 143 km wide. NASA / GSFC / ASU

Posidonius Crater

Posidonius Crater, with its rille system named Rimae Posidonius. This oblique view of the 95-km-wide crater comes from the Lunar Reconnaissance Orbiter. NASA / GSFC / ASU

Hausen Crater Central Peaks

Hausen Crater Central Peaks – Hills at the center of Hausen Crater, as seen by the Lunar Reconnaissance Orbiter. The crater is nearly four kilometers deep. At high resolution, the angle and details visible in this image–right down to individual boulders–offer a moonwalker’s perspective. NASA / GSFC / ASU

This article originally appeared as a guest post on The Planetary Society site.


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A Spin Through the Inner Solar System

More than 50 years of planetary exploration have yielded a rich harvest of data, including many volumes of pictures. These images have revealed the faces of nearly all the nearby worlds, which have turned out to be both forboding and inviting, alien and familiar. Everywhere there is beauty.

We have enough images, in fact, that for many planets, moons, and small bodies we can construct full, global maps. This has been true for places like Mars for decades. For others, such as Mercury and the asteroid Vesta, it has become possible only in the past few years, thanks to the ongoing work of robotic scouts throughout the Solar System and the dedicated people on Earth who fly them.

Following is a series of short videos showing the worlds of the inner Solar System spinning to show their various faces. With two exceptions, each video resulted from taking thousands of individual observations from spacecraft, and combining the data into a 3D computer model.

This look at the Sun comes from the Solar Dynamics Observatory in orbit around the Earth. It shows the Sun as it appeared over the course of the past few days, as seen by sensors tuned to three different wavelengths of extreme ultraviolet light. Later in the decade, new missions will actually fly close to the Sun for even more detailed shots.

This globe comes from thousands of obesrvations by the MESSENGER spacecraft in orbit around Mercury. MESSENGER carries cameras that can observe many wavelenths of light as it bounces off the planet, in order to spy different minerals on the surface. This map shows greatly exaggerated colors in order to highlight the diversity of geology.

Venus is entirely shrouded in dense clouds, of course, but in the 1990s the Magellan spacecraft mapped the surface anyway using radar. The video highlights two large “continents,” or highlands, Aphrodite Terra and Ishtar Terra, the Maxwell Montes mountain range, and Maat Mons, a large, currently dormant volcano. Notice the motion of the clouds at the beginning. Venus is the one inner planet that rotates “backwards” to the other planets.

This map of the moon comes from thousands of photos sent by the Lunar Reconnaissance Orbiter. Each was taken when the Sun was nearly directly overhead at the moment the image was taken. When all stitched together, they make a globe of striking crispness and clarity.

Here is Mars, showing both the actual relief of its surface features, and a version where the topographical data has been wildly stretched to draw out the planet’s complex landscapes.

Finally, we have Vesta, a tiny place compared to these other worlds, but a giant among the members of the asteroid belt. This rotation is not a computer model, but a series of images stitched together from photos sent by the Dawn spacecraft.

These spinning globes show how much we’ve explored. On the other hand, they serve as a reminder of how much remains unseen. There is no rotating map of the largest asteroid Ceres, or of Pluto. That situation will change next year. However, there are many other worlds in the outer Solar System where there are still blank spaces on the map. Sadly, there are no missions even on the drawing board to explore most of them.

There is still much to do.

This article originally appeared as a guest post on The Planetary Society site.


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Mission to a Star

There are things that we see every day, but that we don’t really see at all. There are objects so common that we pay them no attention—even the most spectacular ones. At the bright center of all such things, I’d say, is the Sun. When was the last time you noticed it, or thought about what it is?

Here is our very own living star. A spacecraft orbiting the Earth called the Solar Dynamics Observatory (SDO) captured this image…today.

Sun Storms in Extreme Ultraviolet

Sun Storms in Extreme Ultraviolet – The limb of the Sun as it appeared at a wavelength of 171 angstroms, as seen in February, 2014 by the Solar Dynamics Observatory. NASA / GSFC / AIA, EVE, HMI

Looking at the Sun in this wavelength of light is a good way to catch coronal loops, arcs of plasma often larger than the entire Earth, that surge along the Sun’s powerful magnetic field lines. The temperature here reaches about 1 million degrees Kelvin (1.8 million Fahrenheit).

SDO monitors the Sun continually. We can even see a time-lapse movie of the star’s motion over the course of several days, a good reminder that the Sun is much more than a static sphere.

SDO is just one member of a fleet of spacecraft, past and present, that have observed the Sun. But most of these have done so from around or near the Earth (with important exceptions, such as the Helios mission in the 1970s).

For all our watching, we remain in the dark about many of the Sun’s secrets. In the next few years, though, two ambitious new missions will set out for the very heart of the Solar System, and will encounter our star close up.

Solar Orbiter

Solar Orbiter – ESA’s Solar Orbiter spacecraft, slated for launch in 2017. ESA / Astrium

The European Space Agency’s Solar Orbiter spacecraft, in collaboration with NASA, will orbit the sun closer than any other so far, as close as 42 million km, just over a quarter of the distance to Earth. After launch in 2017, Solar Orbiter will swing by Venus and the Earth for gravitational speed boosts before finally reaching operational orbit three-and-a-half years later.

From there, it will chart the innermost regions of the solar system, with clear views of the Sun’s poles.

According to ESA, the spacecraft will be in a great position to observe the links between the sun’s surface, its corona and heliosphere. From the mission site: “Solar Orbiter will be used to examine how the Sun creates and controls the heliosphere, the vast bubble of charged particles blown by the solar wind into the interstellar medium. The spacecraft will combine in situ and remote sensing observations to gain new information about the solar wind, the heliospheric magnetic field, solar energetic particles, transient interplanetary disturbances and the Sun’s magnetic field.”

The spacecraft carries 21 sensors, many of which operate from behind a carefully-designed heat shield that will protect the ship’s workings from temperatures as high as 520°C. A key ingredient in the shield will be ‘Solar Black,’ a type of calcium phosphate derived from burnt bone charcoal, the same material often used in prehistoric cave paintings.

Solar Probe Plus

Solar Probe Plus – NASA’s Solar Probe Plus, slated for launch in 2018. NASA / JHUAPL

The very next year after Solar Obiter departs, another Sun-bound spacecraft is slated for launch. If it successfully completes the mission design reviews now underway, Solar Probe Plus will be the first to actually fly right into the Sun’s atmosphere, the corona. It will pass within 8.5 solar radii of the Sun itself. The goal is to understand how the corona is heated and how the solar wind is accelerated.

Solar Probe Plus will be undertaking quite an odyssey. It will loop around the inner solar system for the better part of a decade, swinging by Venus not once but seven times before finally making a close approach to the Sun in 2024. Once there, the Sun’s tremendous gravity will accelerate the spacecraft to an astounding 724,000 kph (450,000 mph). At that speed you could travel from Los Angeles to San Diego in less than a second. In that place the temperatures, and the views, will be truly terrific.

If they succeed, both of these missions should open our eyes to the Sun in a whole new way.

This article originally appeared as a guest post on The Planetary Society site.


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