Category: Solar System

NASA releases new mosaics of Saturn moon Titan

Infrared instrument successfully peered through atmospheric haze to reveal surface features.

Using six separate images of Saturn’s largest moon Titan collected by the Cassini orbiter over 13 years, NASA released new mosaics  showing the moon in stunning detail.

The images were collected by Cassini’s Visual and Infrared Mapping Spectrometer (VIMS) instrument, which observed in infrared wavelengths, enabling it to penetrate Titan’s hazy atmosphere, a feat not possible in visible wavelengths.

While this is not the first time VIMS images were used to create mosaics, it is the first time mission scientists produced mosaics that do not show the prominent seams that result from putting together images taken at different times, with a variety of lighting conditions and from a variety of angles.

By reanalyzing the VIMS data and processing the mosaics by hand, mission scientists successfully created the first seamless images of Saturn’s large 3,200-mile- (5,150-km-) wide moon, sometimes viewed as an analogue of early Earth.

Clearly visible in the colorful mosaics are Titan’s complex, varied surfaces, including seas of liquid hydrocarbons, icy deposits, and dunes that contain organic compounds.

“With the seams now gone, this new collection of images is by far the best representation of how the globe of Titan might appear to the casual observer if it weren’t for the moon’s hazy atmosphere,” mission scientists noted in a public statement.

Titan’s thick atmosphere, which contains a high percentage of nitrogen, conceals these diverse terrains. Small particles known as aerosols in the moon’s upper atmosphere scatter visible light, allowing viewers to see only a hazy orange sphere.

Atmospheric scattering and light absorption are much weaker in infrared wavelengths, which is why VIMS was able to obtain detailed photos of Titan’s surface.

Other than Earth, Titan is the only solar system object known to host liquids on its surface.

VIMS’s unique images of Titan will serve as a starting point for future missions observing the moon in the infrared in higher resolutions.

A proposed return to Titan, dubbed the Dragonfly mission, is one of two finalists in NASA’s New Frontiers program. To determine Titan’s habitability for life as we know it, Dragonfly would study the moon’s surface via a robotic minihelicopter.

If selected, Dragonfly will launch in 2025.

Cassini scientists also released a map of Titan showing latitudes, longitudes, and labeled surface features.

New ‘ghost dunes’ uncovered on Mars

Astronomers have found hundreds of never before seen ghost dunes on the Martian surface.

Researchers from the University of Washington have discovered hundreds imprints of ancient sand piles — known as ghost dunes — on Mars’ surface, according to a recent study in the Journal of Geophysical Research.

The team found the remains in two different locations on the Red Planet, a discovery that could give insight into the world’s past climate.

The dunes formed back when the planet had both flowing water and active volcanoes. Such natural processes covered the formations with sediment about two billion years ago and slowly hardened them over time. Then, harsh winds blew the sand away from the inside and left the imprints behind.

This is not the first time astronomers have discovered ghost dunes on Mars — there are some in the Medusa Fossae formation for instance — but the new research identified 300 previously undiscovered ones in both the Hellas Basin and the Noctis Labyrinthus.

They made the discovery by looking at images of the Mars’ surface and then scanning the pictures for clusters of crescent-shaped pits. That unique shape indicates the dunes were “barchan dunes,” which form on flat surfaces with unidirectional winds.

Studying the orientation allowed scientists to determine that the winds came from the north and steadily pushed the dunes south. That is strictly different than the wind direction today, suggesting that environmental conditions on the planet shifted over time.

“One of the cool things about the ghost dunes is that they tell us, for sure, that the wind on Mars was different in the ancient past, when they formed,” said lead author Mackenzie Day, a researcher at the University of Washington, in a statement. 

In addition, the team managed to figure out how big the dunes were. The ones in the Hellas Basin averaged 250 feet tall, while the ones in the Noctis Labyrinthus were roughly half that size.

The finding is interesting, and the researchers hope to follow up on their study could give new insight into the rocky landscape. There is also a chance that the wind did not fully clear the molds and that some ancient sand could still be stuck in them.

“There is probably nothing living there now,” added Day, according to Atlas Obscura. “But if there ever was anything on Mars, this is a better place on average to look.”

Near-Earth asteroid is actually a binary system

Discovery gives scientists opportunity to better understand binary asteroids’ formation processes and compositions.

A near-Earth asteroid discovered last year is actually a binary system of two objects that orbit one another, according to observations conducted by three of the world’s largest radio telescopes.

Asteroid 2017 YE5, found by the Morocco Oukaimeden Sky Survey on December 21, 2017, is the fourth “equal mass” binary near-Earth asteroid ever found. “Equal mass” binaries are systems of two objects almost identical in size and mass orbiting but not touching one another.

Exactly six months after 2017 YE5’s discovery, on June 21 of this year, the asteroid made its closest approach to Earth for the next 170 years, coming about 16 times the Earth-Moon distance, or 3.7 million miles (six million km) of our planet.

Because nothing was known about the asteroid’s physical properties, researchers at three separate observatories took advantage of its close approach and turned their radio telescopes to the object.

NASA’s Goldstone Solar System Radar (GSSR), located in California, found the first signs that the asteroid is really two objects, revealing two lobes.  Scientists could not tell whether the lobes were or were not attached to one another until the objects’ rotations revealed a gap between them.

After being alerted to the fact that 2017 YE5 showed signs of being a binary, scientists at the Arecibo Observatory in Puerto Rico and at the Green Bank Observatory (GBO) in West Virginia set up their radio telescopes to work together to study the object through an arrangement known as a “bi-static radio configuration.” The setup involved Arecibo transmitting a radio signal and Green Bank receiving the return signal.

The joint effort confirmed the asteroid’s status as a binary system, revealing the two objects orbit each other once every 20 to 24 hours.

Observations of the asteroid in visible light by astronomers at the Center for Solar System Studies in Rancho Cucamonga, California, confirmed the rotation data.

Radar data revealed the objects do not reflect the level of sunlight typical of rocky asteroids, meaning they have dark surfaces. The two objects show different levels of radar reflectivity, an unusual feature for binary asteroid systems. Differences in their radar reflectivity could indicate they have different density levels, surface roughness, and near-surface compositions.

According to scientists’ estimates, approximately 15 percent of near-Earth asteroids 650 feet (200 meters) or larger are binaries, but most consist of a larger object orbited by a smaller one rather than two equal-mass bodies. Another 15 percent of near-Earth asteroids this size or larger are contact binaries, in which two objects of roughly the same size touch one another while orbiting each other.

As a next step, researchers hope to determine the densities of 2017 YE5’s two components by analysis of both radar and optical observations.

 

First global maps of Pluto and Charon published

Maps created in painstaking process from digital images captured by New Horizons’ cameras.

Using images and data returned by NASA’s New Horizons spacecraft in 2015, members of the mission science team have created and published global topographic maps of Pluto and its largest moon Charon.

Led by New Horizons senior staff scientist Paul Schenk of the Lunar and Planetary Institute (LPI), the scientists embarked on the labor-intensive project by gathering all the images taken by the spacecraft’s Long Range Reconnaissance Imager (LORRI) and Multispectral Visible Imaging Camera (MVIC).

They then assembled mosaics for both worlds, carefully aligning surface features in overlapping images. For each region, the scientists used digital analysis of photos taken by both cameras to  create topographic maps. These maps were then integrated into complete topographic maps for both Pluto and Charon.

Over the year-and-a-half during which New Horizons sent back its Pluto data, the researchers were able to create higher quality geographic and topographic maps.

In the final product, each area on Pluto and Charon lit by the Sun is depicted in the highest possible resolution. Individual elevations and the wide variety of terrains on both worlds are clearly visible.

On the Pluto map, viewers can see the steep, icy tops of the planet’s highest mountains, known as the Tenzig Montes range. Located to the southwest of the left side of Pluto’s heart feature, a nitrogen glacier known as Sputnik Planitia, these mountains have slopes of 40 degrees or greater.  The tallest peak sits 3.7 miles (six km) above the mountain range’s base.

Tenzig Montes’s mountains are made up of hard water ice, the only ice powerful enough to hold them up. Other volatile ices on Pluto’s surface, such as methane and nitrogen ice, are not strong enough to hold up such structures and keep them from collapsing.

Several large-scale features not visible in the global mosaic map can be seen in the topographic map. Among these are differences in ice depth in the center versus the outer edges of Sputnik Planitia. Ice depth at the center of the 625-mile (1,000-km) glacier extends 1.5 miles (2.5 km) while at the outer edges reaches as far as 2.2 miles (3.5 km) below Pluto’s sea level, also known as its mean elevation.

Also visible in the topographic map are highly eroded areas of ridges and troughs stretching north to south for about 2,000 miles (3,000 km) close to Sputnik Planitia’s western edge. While this feature is considered evidence of ancient fracturing, scientists do not know why such fracturing would have occurred only in this one area.

Mountain ridges reaching heights between 2.5 and 3.1 miles (four and five km) are also seen on Charon. Scientists believe these formed when the large moon’s outer crust fractured as a subsurface ocean froze.

Fractured terrain and blocky regions may have been caused by cryovolcanism. Trouphs up to 8.7 miles deep (14 km) are seen near Charon’s north pole and in its equatorial regions.

Available for use by the scientific community and the public, the maps have been archived with NASA’s Planetary Data System.