What Is The Surface of Neptune Like?

Neptune Hurricanes
The "surface" of Neptune, its uppermost layer, is one of the most turbulent and active places in the Solar System. Credit: NASA/JPL

As a gas giant (or ice giant), Neptune has no solid surface. In fact, the blue-green disc we have all seen in photographs over the years is actually a bit of an illusion. What we see is actually the tops of some very deep gas clouds, which in turn give way to water and other melted ices that lie over an approximately Earth-size core made of silicate rock and a nickel-iron mix. If a person were to attempt to stand on Neptune, they would sink through the gaseous layers.

As they descended, they would experience increased temperatures and pressures until they finally touched down on the solid core itself. That being said, Neptune does have a surface of sorts, (as with the other gas and ice giants) which is defined by astronomers as being the point in the atmosphere where the pressure reaches one bar. Because of this, Neptune’s surface is one of the most active and dynamic places in entire the Solar System.

Continue reading “What Is The Surface of Neptune Like?”

Feast Your Mind on This: Strange “Brain Terrain” on Mars

HiRISE image of lobate landforms called "brain terrain" that wrap around a small hill on Mars

It doesn’t take much thought to understand why this landscape on Mars is called “brain terrain” — the swirling lobes of ice, part of a large glacial deposit in Mars’ northern hemisphere, uncannily resemble the texture of a brain — or at the very least a brain coral!

What causes this strange landscape? Find out below:

It’s suggested that brain terrain is the result of the thermal stress and contraction, followed by sublimation, of these large ice deposits, laid down during a mid-latitude glaciation period ten to 100 million years ago. (Read more in this 2009 paper by Brown University’s Joseph Levy et al.)

This image was obtained by the HiRISE camera aboard the Mars Reconnaissance orbiter on August 23, 2013. See the original RGB color scan here.

Source: University of Arizona’s HiRISE site

MESSENGER Sees a Smoother Side of Mercury

A high-resolution view of a "silky" surface on Mercury

During its two years in orbit around Mercury — as well as several more years performing flybys — the MESSENGER spacecraft has taken over 150,000 images of the innermost planet, giving us a look at its incredibly rugged, Sun-scoured surface like never before. But not all areas on Mercury appear so harsh — it has its softer sides too, as seen above in an image released earlier today.

Here we see the smooth walls, floor and upper surfaces around an irregular depression on Mercury in high definition. The velvety texture is the result of widespread layering of fine particles, because unlike many features on Mercury’s  ancient surface this rimless depression wasn’t caused by an impact from above but rather explosively escaping lava from below — this is the rim of a volcanic vent, not a crater!

Previous images have been acquired of this irregularly-shaped depression but this is the highest resolution view MESSENGER has captured to date — about 26 meters per pixel.

A wide-angle view of the same depression, captured in July 2012
A wide-angle view of the same depression, captured by MESSENGER in July 2012

The full depression, located northeast of the Rachmaninoff basin, is about 36 km (22 miles) across at its widest. It’s surrounded by a smooth blanket of high-reflectance material — explosively ejected volcanic particles from a pyroclastic eruption that spread over the surface like snow.

Other similar vents have been found on Mercury, like this heart-shaped one in Caloris basin. The smooth, bright surface material is a telltale sign of a volcanic outburst, as are the rimless, irregular shapes of the vents.

The numerous small craters that are seen inside the vent and on the smooth surrounding surfaces would be from meteorite impacts that occurred well after the eruption.

On March 17, 2011, MESSENGER became the first spacecraft ever to orbit the planet Mercury. It is capable of continuing orbital operations until early 2015. Find out more about the mission here.

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


Are Venus’ Volcanoes Still Active?

Artist’s impression of an active volcano on Venus (ESA/AOES)

Incredibly dense, visually opaque and loaded with caustic sulfuric acid, Venus’ atmosphere oppresses a scorched, rocky surface baking in planet-wide 425 ºC (800 ºF) temperatures. Although volcanoes have been mapped on our neighboring planet’s surface, some scientists believe the majority of them have remained inactive — at least since the last few hundreds of thousands of years. Now, thanks to NASA’s Pioneer Venus and ESA’s Venus Express orbiters, scientists have nearly 40 years of data on Venus’ atmosphere — and therein lies evidence of much more recent large-scale volcanic activity.

The last six years of observations by Venus Express have shown a marked rise and fall of the levels of sulfur dioxide (SO2) in Venus’ atmosphere, similar to what was seen by NASA’s Pioneer Venus mission from 1978 to 1992.

These spikes in SO2 concentrations could be the result of volcanoes on the planet’s surface, proving that the planet is indeed volcanically active — but then again, they could also be due to variations in Venus’ complex circulation patterns which are governed by its rapid “super-rotating” atmosphere.

“If you see a sulphur dioxide increase in the upper atmosphere, you know that something has brought it up recently, because individual molecules are destroyed there by sunlight after just a couple of days,” said Dr. Emmanuel Marcq of Laboratoire Atmosphères in France, lead author of the paper, “Evidence for Secular Variations of SO2 above Venus’ Clouds Top,” published in the Dec. 2 edition of Nature Geoscience.

“A volcanic eruption could act like a piston to blast sulphur dioxide up to these levels, but peculiarities in the circulation of the planet that we don’t yet fully understand could also mix the gas to reproduce the same result,” added co-author Dr Jean-Loup Bertaux, Principal Investigator for the instrument on Venus Express.

The rise and fall of sulphur dioxide in the upper atmosphere of Venus over the last 40 years, expressed in units of parts per billion by volume. Credits: Data: E. Marcq et al. (Venus Express); L. Esposito et al. (earlier data); background image: ESA/AOES

Because Venus’ dense atmosphere whips around the planet at speeds of 355 km/hour (220 mph), pinpointing an exact source for the SO2 emissions is extremely difficult. Volcanoes could be the culprit, but the SO2 could also be getting churned up from lower layers by variations in long-term circulation patterns.

Read: Venus Has a Surprisingly Chilly Layer

Venus has over a million times the concentration of sulfur dioxide than Earth, where nearly all SO2 is the result of volcanic activity. But on Venus it’s been able to build up, kept stable at lower altitudes where it’s well shielded from solar radiation.

Regardless of its source any SO2 detected in Venus’ upper atmosphere must be freshly delivered, as sunlight quickly breaks it apart. The puzzle now is to discover if it’s coming from currently-active volcanoes… or something else entirely.

“By following clues left by trace gases in the atmosphere, we are uncovering the way Venus works, which could point us to the smoking gun of active volcanism,” said Håkan Svedhem, ESA’s Project Scientist for Venus Express.

Read more on the ESA release here.

Titan Shines in Latest Cassini Shots

Color-composite raw image of Titan’s southern hemisphere. Note the growing south polar vortex. (NASA/JPL/SSI/Jason Major)

Last Thursday, November 29, Cassini sailed past Titan for yet another close encounter, coming within 1,014 kilometers (603 miles) of the cloud-covered moon in order to investigate its thick, complex atmosphere. Cassini’s Visible and Infrared Mapping Spectrometer (VIMS), Composite Infrared Spectrometer (CIRS) and Imaging Science Subsystems (ISS) instruments were all busy acquiring data on Titan’s atmosphere and surface… here are a couple of color-composites made from raw images captured in visible light channels as well as some of the more interesting monochrome raw images. Enjoy!

The structure of Titan’s upper-level hazes, which extend ten times the height of Earth’s atmosphere. (NASA/JPL/SSI)

Cassini captured this view of Titan’s crescent during its approach, from a distance of 193,460 kilometers (NASA/JPL/SSI/Jason Major)

Cassini’s continuum filter (CB3) allows it to image Titan’s surface. The dark areas are vast fields of hydrocarbon sand dunes (NASA/JPL/SSI)

These images have not been validated or calibrated by NASA or the mission team.

Read more about the T-88 flyby here.

Mercury’s Many Colors

Although composited from expanded wavelengths of light, this wide-angle image from NASA’s MESSENGER spacecraft shows the amazing variation of colors and tones to be found on Mercury’s Sun-scoured surface.

This scene lies between Mercury’s Moody and Amaral craters, spanning an area of about 1200 km (745 miles). The patch of dark blue Low Reflectance Material (LRM) in the upper left of the image and the bright rayed crater on the right make this a diverse view of Mercury’s surface. Note the curious small, dark crater just below the bright rayed crater on the right.

Dark LRM material is thought to indicate the presence of a mineral called ilmenite, which is composed of iron and titanium and has been revealed through volcanic, cratering and erosion processes.

More Mercury images: Postcards from the (Inner) Edge

Did you know that until MESSENGER arrived in 2008 half of Mercury had never been seen? And that although Mercury is the closest planet to the Sun there may still be water ice on its surface? Learn more about these and other fascinating facts about Mercury here.

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


Postcards From The (Inner) Edge

As the world turns its gaze outward in anticipation of the arrival of Mars Science Laboratory — with its hair-raising “seven minutes of terror” landing — let’s take a moment to look back inward, where MESSENGER is still faithfully orbiting the first rock from the Sun, Mercury, and sending back images that could only have been imagined just a few years ago.

The image above shows the graben-gouged terrain around Balanchine crater, within Mercury’s vast Caloris Basin impact crater. Named for the co-founder of the New York City Ballet, Balanchine crater is 41 km (25.5 miles) in diameter and filled with the curious erosion features known as hollows. Graben — basically sunken troughs in the surface — are the result of extensional forces that have pulled sections of the planet’s upper crust apart.

This image shows the peak-ring structure located within the much larger crater Rustaveli, which is 180 km (112 miles) in diameter. One of the more recently-named craters (the IAU convention for new features on Mercury has them titled after renowned artists, writers and composers from history) Rustaveli is named for a 12th-century Georgian poet who wrote the epic “The Knight in the Panther’s Skin”. The crater that now bears his namesake is located on Mercury’s northern hemisphere.

These two craters — also located within Caloris Basin — don’t yet have names but are no less interesting. Their overlapping positions works like an optical illusion, making the newer,sharper-edged crater on the right seem to almost float above the surface. The false-color of the image highlights the difference in surface composition of the two craters, which are both about 40 km (24 miles) wide. (The Caloris Basin in which they reside, however, is one of the largest known impact sites in our solar system, measuring at 1550 km — 963 miles — across!)

Now we zoom out for a wider view of our solar system’s second-densest planet (Earth is the first) and take a look at an image that’s night and day — literally! This is Mercury’s terminator, the twilit dividing line between night and day. More than just making a pretty picture, data on this transition is valuable to scientists as some atmospheric phenomena can only be observed at the terminator, such as the interaction between surface dust and charged particles from the Sun (which, at less than half the distance to the Sun than we are, Mercury is constantly bathed in.)

And now to zoom back in, we get a good look at an unnamed central-peaked crater about 85 km (52 miles) across in an oblique view  that highlights the hollows and depressions within its floor. Acquired as part of what’s called a “targeted observation”, high-resolution images like this (79 meters/pixel) allow scientists to closely investigate specific features — but sadly there’s just not enough mission time to image all of Mercury at this level of detail.

On March 17, 2011 (March 18, 2011, UTC), MESSENGER became the first spacecraft ever to orbit Mercury. The mission has provided the first data from Mercury since Mariner 10, over 30 years ago. After over 1,000 orbits, 98 percent of Mercury is now imaged in detail, allowing us to know more about our solar system’s innermost world than ever before.

Keep up with MESSENGER updates (and the latest images) on the mission website here.

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

The Bright and Dark Side of Vesta’s Craters


Bright craters, dark craters… craters shaped like butterflies… they’re all represented here in a panorama made from images acquired by NASA’s Dawn spacecraft, currently in orbit around the asteroid Vesta.

I stitched two images together (using a third for gap fill-in) that were originally acquired by Dawn’s framing camera in October 2011 and released last week. Because the angle of sunlight is pretty close to straight-on, there’s not a whole lot of relief in the original images so I bumped that contrast up a bit as well, to help bring out Vesta’s terrain.

The dark crater in the center is Laelia, and it’s surrounded by smaller dark impact craters as well… most notably one that displays dramatic rays of dark material. At top right is the much larger crater Sextilia, which has bright material revealed along its inner rim.

Near the lower left edge, just horizontal from Laelia, is the butterfly-shaped Helena crater. It shows both bright and dark material, the latter of which can be seen slumping into the crater as well as outward from its rim. Helena is approximately 22 kilometers (14 miles) in diameter. (There’s a scale at the lower right showing a 10-km / 6.2-mile-wide span.)

The images were acquired during the HAMO (high-altitude mapping orbit) phase of the mission.

On Thursday, May 10, NASA will host a news conference at 11 a.m. PDT (2 p.m. EDT) to present a new analysis of the giant asteroid Vesta using data from the agency’s Dawn spacecraft. The event will be broadcast live on NASA Television and streamed on the agency’s website. For streaming video, downlink and scheduling information visit: http://www.nasa.gov/ntv.

The event will also be streamed live on Ustream with a moderated chat available at http://www.ustream.com/nasajpl2. Questions may also be asked via Twitter using the hashtag #asknasa.The event will be held at NASA Headquarters in Washington, broadcast live on NASA Television and streamed on the agency’s website. For NASA TV streaming video, downlink and scheduling information, visit: http://www.nasa.gov/ntv.

Image credit: NASA/ JPL-Caltech/ UCLA/ MPS/ DLR/ IDA. Edited by J. Major.

This artist's concept shows NASA's Dawn spacecraft orbiting the giant asteroid Vesta. (NASA/JPL-Caltech)

Messages from Mercury

MESSENGER's view from Mercury's south pole


It’s been just over two months since the MESSENGER spacecraft successfully entered orbit around Mercury, back on March 18, and it’s been enthusiastically returning image after image of our solar system’s innermost planet at a unprecedented rate. Which, of course, is just fine with us!

The image above shows Mercury’s southern hemisphere and the bright rays of the 50-km-wide crater Han Kan. It was acquired on May 17, 2011.

Below are more recent images from MESSENGER… some of which show regions and features that have never previously been mapped – or even named!

Unnamed double peak-ring basin. Acquired May 13.
Detail of the mountains that make up the rim of Caloris Basin. Acquired May 5.
Narrow-angle camera view of the 100-km-wide Atget crater. Acquired May 10.
Color map of Mercury's surface. The bright crater is Snorri (21km wide). Acquired April 15.

Click on the images to see more detail on the MESSENGER mission site.

MESSENGER’s orbit about Mercury is highly elliptical, taking it 200 kilometers (124 miles) above its northern surface at the closest pass and 15,193 kilometers (9,420 miles) away from the south pole at furthest. Check out this video showing an animation of how a typical MESSENGER orbit would be executed.

Image credits: Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington.

The MESSENGER spacecraft is the first ever to orbit the planet Mercury, and the spacecraft’s seven scientific instruments and radio science investigation are unraveling the history and evolution of the Solar System’s innermost planet. During the one-year primary mission, MDIS is scheduled to acquire more than 75,000 images in support of MESSENGER’s science goals.