Category Archives: Moons

Beresheet Impact Site Found

Seeing “humps” instead of craters? Click here.

NASA: The photo above shows the landing site of the Israeli Beresheet spacecraft on a region of the Moon called Sea of Serenity, or Mare Serenitatis in Latin. On April 11, 2019, SpaceIL, a non-profit organization, attempted to land its spacecraft in this ancient volcanic field on the nearside of the Moon. After a smooth initial descent, Beresheet made a hard landing on the surface.

As soon as its orbit placed NASA’s Lunar Reconnaissance Orbiter (LRO) over the landing site on April 22, 2019, LRO imaged Beresheet’s impact site. The LRO Camera (LROC) consists of three imagers: a seven-color Wide Angle Camera (WAC) and two black-and-white Narrow Angle Cameras (NAC) mounted on the LRO, which has been studying the Moon from orbit for a decade. NAC captured the Beresheet impact photo.

LROC took this image from 56 miles (90 kilometers) above the surface. The cameras captured a dark smudge, about 10 meters wide, that indicates the point of impact. The dark tone suggests a surface roughened by the hard landing, which is less reflective than a clean, smooth surface.

From so far away, LROC could not detect whether Beresheet formed a surface crater upon impact. It’s possible the crater is just too small to show up in photos. Another possibility is that Beresheet formed a small indent instead of a crater, given its low angle of approach (around 8.4 degrees relative to the surface), light mass (compared to a dense meteoroid of the same size), and low velocity (again, relative to a meteoroid of the same size; Beresheet’s speed was still faster than most speeding bullets).

The light halo around the smudge could have formed from gas associated with the impact or from fine soil particles blown outward during Beresheet’s descent, which smoothed out the soil around the landing site, making it highly reflective.

There are many clues that we’re actually looking at a man-made crater instead of a meteoroid-caused one. This is an important consideration, since the Moon, having no atmosphere, is constantly bombarded by space rocks that leave craters.

Most importantly, we knew the coordinates of the landing site within a few miles thanks to radio tracking of Beresheet, and we have 11 “before” images of the area, spanning a decade, and three “after” images. In all of these images, including one taken 16 days before the landing, we saw only one new feature of the size Beresheet would have created.

Existing mathematical models helped us estimate the size and shape of the crater that would have formed if an object of Beresheet’s mass and velocity struck the surface. We also referenced craters created by similar-size spacecraft (GRAILLADEERanger) that have struck the Moon at about the same speed, and we saw that the white tail stretching from the landing halo towards the south is a shape that’s consistent with Beresheet’s southward descent trajectory and angle of approach.

For the before image above, we used a photo from December 16, 2016.  This is because the lighting conditions that day, based on the angle at which the Sun would have illuminated the Moon at that particular time in its orbit, were the most similar to the April 22 image. Because LRO was beyond the horizon during Beresheet’s descent and landing, it couldn’t capture a photo until its orbit brought it nearby 11 days later. LRO passes over the lunar poles with each revolution. Meanwhile, the Moon rotates on its axis below the spacecraft, allowing LRO to pass over every part of the Moon twice a month (once during lunar night and once during lunar day). LROC may take more images of the landing site when it passes the same area again on May 19.

Efforts are ongoing to bounce laser pulses from the Lunar Orbiter Laser Altimeter, also on board LRO, to measure the return from the Laser Retroreflector Array of small corner cube mirrors. This instrument was provided by NASA’s Goddard Space Flight Center and was installed on the top deck of the Beresheet spacecraft. Attempts are ongoing to examine if the retroreflector may have survived the impact.

Images: NASA/GSFC/Arizona State University

Phobos Temperatures

The surprising (to me at least) findings from temperature observations of the Martian moon Phobos. The infrared signatures seem to shows the moon appears to get warm it is at times. I’m sure the warmth may be fleeting the but we are talking about nice warm and therefore comfortable summer temperatures for most of us here on Earth.

NASA’s caption: These are three different views of the Martian moon Phobos, as seen by NASA’s 2001 Mars Odyssey orbiter using its infrared camera, Thermal Emission Imaging System (THEMIS). Each color represents a different temperature range.

The annotated version of this image labels each of these views with the dates when they were imaged by THEMIS. The two views on the left were taken while Phobos was in a half-moon phase, which is better for studying surface textures. The third, on the far-right, was taken in a full-moon phase, which is better for studying material composition.

A scale bar on the annotated image ranges from 150 to 300 degrees Kelvin, or -190 degrees Fahrenheit (-123 degrees Celsius) to 80 degrees Fahrenheit (27 degrees Celsius).

NASA’s Jet Propulsion Laboratory in Pasadena, California, manages the 2001 Mars Odyssey mission for NASA’s Science Mission Directorate in Washington. THEMIS was developed by Arizona State University in Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing.

The THEMIS investigation is led by Philip Christensen at ASU. The prime contractor for the Odyssey project, Lockheed Martin Space in Denver, developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of Caltech in Pasadena.Image Credit:NASA/JPL-Caltech/ASU/SSI

The Moon is Losing Water?

The Moon does have miniscule traces of water (H2O), but apparently enough water to lose, I will let NASA explain:

Researchers from NASA and the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, report that streams of meteoroids striking the Moon infuse the thin lunar atmosphere with a short-lived water vapor.

The findings will help scientists understand the history of lunar water — a potential resource for sustaining long term operations on the Moon and human exploration of deep space. Models had predicted that meteoroid impacts could release water from the Moon as a vapor, but scientists hadn’t yet observed the phenomenon. 

Now, the team has found dozens of these events in data collected by NASA’s Lunar Atmosphere and Dust Environment Explorer. LADEE was a robotic mission that orbited the Moon to gather detailed information about the structure and composition of the thin lunar atmosphere, and determine whether dust is lofted into the lunar sky

“We traced most of these events to known meteoroid streams, but the really surprising part is that we also found evidence of four meteoroid streams that were previously undiscovered,” said Mehdi Benna of NASA’s Goddard Space Flight Center in Greenbelt, Maryland, and the University of Maryland Baltimore County. Benna is the lead author of the study, published in Nature Geosciences.

The newly identified meteoroid streams, observed by LADEE, occurred on Jan. 9, April 2, April 5 and April 9, 2014.

There’s evidence that the Moon has water (H2O) and hydroxyl (OH), a more reactive relative of H2O. But debates continue about the origins of the water, whether it is widely distributed and how much might be present.

“The Moon doesn’t have significant amounts of H2O or OH in its atmosphere most of the time,” said Richard Elphic, the LADEE project scientist at NASA’s Ames Research Center in California’s Silicon Valley. “But when the Moon passed through one of these meteoroid streams, enough vapor was ejected for us to detect it. And then, when the event was over, the H2O or OH went away.”

Lunar scientists often use the term “water” to refer to both H2O and OH. Figuring out how much H2O and how much OH are present is something future Moon missions might address.

LADEE, which was built and managed by NASA’s Ames Research Center in California’s Silicon Valley, detected the vapor using its Neutral Mass Spectrometer, an instrument built by Goddard. The mission orbited the Moon from October 2013 to April 2014 and gathered detailed information about the structure and composition of the lunar atmosphere, or more correctly, the “exosphere” – a faint envelope of gases around the Moon.

To release water, the meteoroids had to penetrate at least 3 inches (8 centimeters) below the surface. Underneath this bone-dry top layer lies a thin transition layer, then a hydrated layer, where water molecules likely stick to bits of soil and rock, called regolith.

From the measurements of water in the exosphere, the researchers calculated that the hydrated layer has a water concentration of about 200 to 500 parts per million, or about 0.02 to 0.05 percent by weight. This concentration is much drier than the driest terrestrial soil, and is consistent with earlier studies. It is so dry that one would need to process more than a metric ton of regolith in order to collect 16 ounces of water.

Because the material on the lunar surface is fluffy, even a meteoroid that’s a fraction of an inch (5 millimeters) across can penetrate far enough to release a puff of vapor. With each impact, a small shock wave fans out and ejects water from the surrounding area.

When a stream of meteoroids rains down on the lunar surface, the liberated water will enter the exosphere and spread through it. About two-thirds of that vapor escapes into space, but about one-third lands back on the surface of the Moon.

These findings could help explain the deposits of ice in cold traps in the dark reaches of craters near the poles. Most of the known water on the Moon is located in cold traps, where temperatures are so low that water vapor and other volatiles that encounter the surface will remain stable for a very long time, perhaps up to several billion years. Meteoroid strikes can transport water both into and out of cold traps.

The team ruled out the possibility that all of the water detected came from the meteoroids themselves.

“We know that some of the water must be coming from the Moon, because the mass of water being released is greater than the water mass within the meteoroids coming in,” said the second author of the paper, Dana Hurley of the Johns Hopkins University Applied Physics Laboratory.

The analysis indicates that meteoroid impacts release water faster than it can be produced from reactions that occur when the solar wind hits the lunar surface.

“The water being lost is likely ancient, either dating back to the formation of the Moon or deposited early in its history,” said Benna.

NASA is leading a sustainable return to the Moon with commercial and international partners to expand human presence in space and bring back new knowledge and opportunities.

By Elizabeth Zubritsky

Image: NASA Goddard/Mehdi Benna/Jay Friedlander

Two New Moons?


Could the data from the Voyager spacecraft still be providing discoveries?  Yes indeed!

Credits: NASA/Erich Karkoschka (Univ. Arizona)

From NASA:

NASA’s Voyager 2 spacecraft flew by Uranus 30 years ago, but researchers are still making discoveries from the data it gathered then. A new study led by University of Idaho researchers suggests there could be two tiny, previously undiscovered moonlets orbiting near two of the planet’s rings.

Rob Chancia, a University of Idaho doctoral student, spotted key patterns in the rings while examining decades-old images of Uranus’ icy rings taken by Voyager 2 in 1986. He noticed the amount of ring material on the edge of the alpha ring — one of the brightest of Uranus’ multiple rings — varied periodically. A similar, even more promising pattern occurred in the same part of the neighboring beta ring.

“When you look at this pattern in different places around the ring, the wavelength is different — that points to something changing as you go around the ring. There’s something breaking the symmetry,” said Matt Hedman, an assistant professor of physics at the University of Idaho, who worked with Chancia to investigate the finding. Their results will be published in The Astronomical Journal and have been posted to the pre-press site arXiv.

Chancia and Hedman are well-versed in the physics of planetary rings: both study Saturn’s rings using data from NASA’s Cassini spacecraft, which is currently orbiting Saturn. Data from Cassini have yielded new ideas about how rings behave, and a grant from NASA allowed Chancia and Hedman to examine Uranus data gathered by Voyager 2 in a new light. Specifically, they analyzed radio occultations — made when Voyager 2 sent radio waves through the rings to be detected back on Earth — and stellar occultations, made when the spacecraft measured the light of background stars shining through the rings, which helps reveal how much material they contain.

They found the pattern in Uranus’ rings was similar to moon-related structures in Saturn’s rings called moonlet wakes.

The researchers estimate the hypothesized moonlets in Uranus’ rings would be 2 to 9 miles (4 to 14 kilometers) in diameter — as small as some identified moons of Saturn, but smaller than any of Uranus’ known moons. Uranian moons are especially hard to spot because their surfaces are covered in dark material.

“We haven’t seen the moons yet, but the idea is the size of the moons needed to make these features is quite small, and they could have easily been missed,” Hedman said. “The Voyager images weren’t sensitive enough to easily see these moons.”

Hedman said their findings could help explain some characteristics of Uranus’ rings, which are strangely narrow compared to Saturn’s. The moonlets, if they exist, may be acting as “shepherd” moons, helping to keep the rings from spreading out. Two of Uranus’ 27 known moons, Ophelia and Cordelia, act as shepherds to Uranus’ epsilon ring.

“The problem of keeping rings narrow has been around since the discovery of the Uranian ring system in 1977 and has been worked on by many dynamicists over the years,” Chancia said. “I would be very pleased if these proposed moonlets turn out to be real and we can use them to approach a solution.”

Confirming whether or not the moonlets actually exist using telescope or spacecraft images will be left to other researchers, Chancia and Hedman said. They will continue examining patterns and structures in Uranus’ rings, helping uncover more of the planet’s many secrets.

“It’s exciting to see Voyager 2’s historic Uranus exploration still contributing new knowledge about the planets,” said Ed Stone, project scientist for Voyager, based at Caltech, Pasadena, California.

Voyager 2 and its twin, Voyager 1, were launched 16 days apart in 1977. Both spacecraft flew by Jupiter and Saturn, and Voyager 2 also flew by Uranus and Neptune. Voyager 2 is the longest continuously operated spacecraft. It is expected to enter interstellar space in a few years, joining Voyager 1, which crossed over in 2012. Though far past the planets, the mission continues to send back unprecedented observations of the space environment in the solar system, providing crucial information on the environment our spacecraft travel through as we explore farther and farther from home.

NASA’s Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, built the twin Voyager spacecraft and operates them for the Heliophysics Division within NASA’s Science Mission Directorate in Washington.


The inner most large moon of Uranus.  Credit: NASA/JPL
The inner most large moon of Uranus. Credit: NASA/JPL

Miranda is probably one of the more bizarre moons in our solar system as we can see in this Voyager image. This inner moon of Uranus is about half rock and water ice. Accounting for the tortured terrain has been a challenge originally it was thought Miranda was shattered and reassembled, however more recently that scenario has been replaced by upwelling of partially melted ices from the interior.

Check out our Miranda page for more about the moon including vital statistics.

Here is the original NASA/JPL caption for the image:

Miranda, innermost of Uranus’ large satellites, is seen at close range in this Voyager 2 image, taken Jan. 24, 1986, as part of a high-resolution mosaicing sequence. Voyager was some 36,000 kilometers (22,000 miles) away from Miranda. This clear-filter, narrow-angle image shows an area about 250 km (150 mi) across, at a resolution of about 800 meters (2,600 feet). Two distinct terrain types are visible: a rugged, higher-elevation terrain (right) and a lower, striated terrain. Numerous craters on the rugged, higher terrain indicate that it is older than the lower terrain. Several scarps, probably faults, cut the different terrains. The impact crater in the lower part of this image is about 25 km (15 mi) across. The Voyager project is managed for NASA by the Jet Propulsion Laboratory.