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. Continue reading “Dancing With Saturn”

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.


Swan Song

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

In Japanese legend, a man once found a tiny girl in a glowing bamboo stalk. After he raised her as his own daughter, one day she broke his heart when she revealed herself to be a princess from the capital of the moon, and announced she had to return home.

She gave her name, Kaguya-hime, to a lunar orbiter launched six years ago this month by the Japan Aerospace Exploration Agency (JAXA). The mission returned volumes of valuable data, not to mention some of the most amazing video and images sent by any space mission in history.

earth from moon
A Rare Gem – The Kaguya lunar orbiter sees the Earth as the spacecraft passes beneath the south pole of the moon. Africa is visible at the right. Credit: JAXA/NHK.

The mission inspired a fascinating multimedia project called Moonbell. This interactive display uses data from Kaguya’s laser altimeter, transforming a detailed map of the moon’s topography into into musical notes and cadence. Moonbell users can choose virtual instruments to play the main notes, representing detailed altitude data, the mid notes, taken from broader topographical information, and the base notes, which follow the average altitude of the lunar landscape. Moonbell will play the resulting celestial music as read from sequential data along Kaguya’s orbital track, or in Free Scratch Mode users can actually draw a line anywhere on the moon’s surface and listen to the sound it produces, like dropping a needle onto a vinyl record.

moonbell screenshot
The Moonbell interactive widget transforms altimeter data from the Kaguya lunar orbiter into music “composed” by the moon itself. Credit: JAXA.

After more than a year of successful work at the moon, the Kaguya mission came to end. Controllers lowered its orbit until it was barely skimming over the gray surface, sending home video and other data until the very end. Finally, on the eleventh of June, 2009, the spacecraft impacted the surface near the south pole.

Here is one of the very last things it saw, a crater partially covered in the polar region’s long shadows.

lunar crater
One Last Look – Just moments before it impacted the surface, the Kaguya lunar orbiter snapped this view of a crater near the south pole. Credit: JAXA/NHK

Kaguya didn’t simply return flat pictures. The very data that made Moonbell possible also allowed explorers to construct 3D models of the terrain by combining visual and altitude data. The following video represents some of the very last of that data, a view of what it would have looked like to ride along with Kaguya as it was pulled down towards its final, permanent encounter with the world it had been exploring all those months.

Moonbell provides yet another way to experience that south polar terrain, the site of Kaguya’s final journey. Drawing a path in Moonbell similar to the one the spacecraft followed during its last orbit, I made a few moments of music “composed” by the moon itself (.mp3 format).

Like its namesake, Kaguya remained on the moon and never returned, but not before gifting us with its swan song of knowledge and images that will be remembered for a very long time.

Parade of Storms

Saturn storms
Several frames showing the north polar region of Saturn. Credit: NASA/JPL/SSI

Several frames showing the north polar region of Saturn, where a series of vortexes are circling the famous hexagonal cloud pattern. Images captured by Cassini June 26, 2013.

The Storm!

The north polar vortex of Saturn, as seen in a series of images captured by the robotic spacecraft Cassini on June 14, 2013. Credit: NASA/JPL/SSI. Animation by Bill Dunford.

The motion of Saturn’s north polar vortex–as seen just last Friday by the robotic spacecraft Cassini. The eye is about 50 times larger than an Earthly hurricane’s, and the clouds at the outer edge are traveling at more than 150 meters per second.

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