A sampling of recent articles, videos, and images from space-related science news items:

Asteroids:

** NASA’s OSIRIS-REx probe gets up close to asteroid Bennu : OSIRIS-REx Breaks Another Orbit Record | NASA

On June 12, NASA’s OSIRIS-REx spacecraft performed another significant navigation maneuver—breaking its own world record for the closest orbit of a planetary body by a spacecraft.

The maneuver began the mission’s new phase, known as Orbital B, and placed the spacecraft in an orbit 680 meters (2,231 feet) above the surface of asteroid Bennu. The previous record—also set by the OSIRIS-REx spacecraft—was approximately 1.3 kilometers (0.8 miles) above the surface.

Upon arrival at Bennu, the team observed particles ejecting into space from the asteroid’s surface. To better understand why this is occurring, the first two weeks of Orbital B will be devoted to observing these events by taking frequent images of the asteroid’s horizon. For the remaining five weeks, the spacecraft will map the entire asteroid using most of its onboard science instruments: the OSIRIS-REx Laser Altimeter (OLA) will produce a full terrain map; PolyCam will form a high-resolution, global image mosaic; and the OSIRIS-REx Thermal Emission Spectrometer (OTES) and the REgolith X-ray Imaging Spectrometer (REXIS) will produce global maps in the infrared and X-ray bands. All of these measurements are essential for selecting the best sample collection site on Bennu’s surface.

Data from these surface studies will be used to find the optimum spot to set down and take a sample to take back to Earth.

The OSIRIS-REx spacecraft is on a seven-year journey to study the asteroid Bennu and return a sample from its surface to Earth. This sample of a primitive asteroid will help scientists understand the formation of the Solar System over 4.5 billion years ago. Sample collection is scheduled for summer of 2020, and the spacecraft will deliver the sample to Earth in September 2023.

An artist's view of OSIRIS-REx investigating asteroid Bennu

“On Jun. 12, 2019, NASA’s OSIRIS-REx spacecraft went into orbit around asteroid Bennu for a second time — breaking its own record for the closest orbit of a planetary body by any spacecraft.” Artwork credits: University of Arizona

** Japan’s Hayabusa2 probe may touch down on asteroid Ryugu again: Approach to the 2nd touchdown – Part 1: observations near the touchdown point – JAXA Hayabusa2 project

Our first touchdown took place this year on February 22. Then as a new challenge for the Hayabusa2 Project, we succeeded in creating an artificial crater using the Small Carry-on Impactor (SCI) on April 5. The last big operation left at asteroid Ryugu is the collection of subsurface material exposed with the creation of the artificial crater. In order to collect this material, we need a second touchdown for which the project has been steadily preparing. At this point, it has not yet been decided whether or not to go ahead with a second touchdown, but here we will introduce our preparations in the “Approach to the second touchdown”.

After the operation to form the artificial crater, the spacecraft descended a total of four times above or near the crater site. These descent operations allowed us to obtain detailed data of the region near the artificial crater. In addition, we succeeded in dropping a target marker in the area close to the artificial crater on May 30. Combined, these operations mean that the situation around the artificial crater is now well understood.

The rocky surface, however, makes it difficult to find a safe spot to set down.

As you can see in [the figure below], asteroid Ryugu is covered with boulders. If we go for a second touchdown, we need to aim for a point close to the target marker which has no obstacles. The project is currently examining this area in detail.

Image of Ryugu surface

“Image taken on June 13, 2019 during the operation PPTD-TM1B. This is a composite of 28 images taken at 7 second intervals starting from 10:58 JST (upper left) to 11:01 (lower right) using the Optical Navigation Camera – Telescopic (ONC-T). The image altitude is about 52m at the start and 108m at the end. The white point in the upper-left center is the target marker. You can see that detailed images have been acquired continuously from the target marker to the edge of the artificial crater, located in the lower-right of the image. (Image credit ※: JAXA, Chiba Institute of Technology, University of Tokyo, Kochi University, Rikkyo University, Nagoya University, Meiji University, University of Aizu, AIST.) “

The Sun:

** Lunar regolith reveals secrets of the early sun: Moon Samples Help Scientists Study Ancient Sun | NASA

Saxena incorporated the mathematical relationship between a star’s rotation rate and its flare activity. This insight was derived by scientists who studied the activity of thousands of stars discovered by NASA’s Kepler space telescope: The faster a star spins, they found, the more violent its ejections. “As you learn about other stars and planets, especially stars like our Sun, you start to get a bigger picture of how the Sun evolved over time,” Saxena said.  

Using sophisticated computer models, Saxena, Killen and colleagues think they may have finally solved both mysteries. Their computer simulations, which they described on May 3 in the The Astrophysical Journal Letters, show that the early Sun rotated slower than 50% of baby stars. According to their estimates, within its first billion years, the Sun took at least 9 to 10 days to complete one rotation.  

They determined this by simulating the evolution of our solar system under a slow, medium, and then a fast-rotating star. And they found that just one version — the slow-rotating star — was able to blast the right amount of charged particles into the Moon’s surface to knock enough sodium and potassium into space over time to leave the amounts we see in Moon rocks today.   

“Space weather was probably one of the major influences for how all the planets of the solar system evolved,” Saxena said, “so any study of habitability of planets needs to consider it.” 

Jupiter:

**  More wonderful views of Jupiter created by citizen scientists from Juno’s raw imagery: Tumultuous Clouds of Jupiter | Mission Juno/Kevin M. Gill

This stunning compilation image of Jupiter’s stormy northern hemisphere was captured by NASA’s Juno spacecraft as it performed a close pass of the gas giant planet. Some bright-white clouds can be seen popping up to high altitudes on the right side of Jupiter’s disk. (The Juno team frequently refers to clouds like these as “pop-up” clouds in image captions.)

Juno took the four images used to produce this color-enhanced view on May 29, 2019, between 12:52 a.m. PDT (3:52 a.m. EDT) and 1:03 a.m. PDT (4:03 a.m. EDT), as the spacecraft performed its 20th science pass of Jupiter. At the time the images were taken, the spacecraft was between 11,600 miles (18,600 kilometers) and 5,400 miles (8,600 kilometers) above Jupiter’s cloud tops, above a northern latitude spanning from about 59 to 34 degrees.

Citizen scientist Kevin M. Gill created this image using data from the spacecraft’s JunoCam imager.

Tumultuous Clouds of Jupiter

“Tumultuous Clouds of Jupiter” – Credits NASA/JPL-Caltech/SwRI/MSSS with image processing by Kevin M. Gill.

Gill also made this overflight of Jupiter’s Great Red Spot:

And Gerald Eichstädt made this terrific time-lapsed tour of Jupiter: Juno’s Perijove-20 Jupiter Flyby, Reconstructed in 125-Fold Time-Lapse – Credit: NASA / JPL / SwRI / MSSS / SPICE / Gerald Eichstädt ©

On May 29, 2019, NASA’s Juno probe successfully performed her Perijove-20 Jupiter flyby. The movie is a reconstruction of the 2 hours and 30 minutes between 2019-05-29T07:20:00.000 and 2019-05-29T09:50:00.000 in 125-fold time-lapse. It is based on 32 of the JunoCam images taken, and on spacecraft trajectory data provided via SPICE kernel files.

In steps of five real-time seconds, one still images of the movie has been rendered from at least one suitable raw image. This resulted in short scenes, usually of a few seconds. Playing with 25 images per second results in 125-fold time-lapse. Resulting overlapping scenes have been blended using the ffmpeg tool. In natural colors, Jupiter looks pretty pale. Therefore, the still images are approximately illumination-adusted, i.e. almost flattened, and consecutively gamma-stretched to the 4th power of radiometric values, in order to enhance contrast and color.

Mars:

** Curiosity detects a curious burst in methane levels: Curiosity Detects Unusually High Methane Levels – NASA JPL

On June 23rd, the Curiosity team reported that during the previous week the

… Mars rover found a surprising result: the largest amount of methane ever measured during the mission – about 21 parts per billion units by volume (ppbv). One ppbv means that if you take a volume of air on Mars, one billionth of the volume of air is methane.

The finding came from the rover’s Sample Analysis at Mars (SAM) tunable laser spectrometer. It’s exciting because microbial life is an important source of methane on Earth, but methane can also be created through interactions between rocks and water.

Curiosity doesn’t have instruments that can definitively say what the source of the methane is, or even if it’s coming from a local source within Gale Crater or elsewhere on the planet.

On June 24th, the team reported results from a

… follow-on methane experiment this past weekend. The results came down early Monday morning: The methane levels have sharply decreased, with less than 1 part per billion by volume detected. That’s a value close to the background levels Curiosity sees all the time.

The finding suggests last week’s methane detection – the largest amount of the gas Curiosity has ever found – was one of the transient methane plumes that have been observed in the past. While scientists have observed the background levels rise and fall seasonally, they haven’t found a pattern in the occurrence of these transient plumes.

“The methane mystery continues,” said Ashwin Vasavada, Curiosity’s project scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California. “We’re more motivated than ever to keep measuring and put our brains together to figure out how methane behaves in the Martian atmosphere.”

** Curiosity’s travels via Leonard David:

  • Curiosity Mars Rover: Eying Teal Ridge Outcrop – June.25.2019

    “Curiosity is still perched on top of Teal Ridge to investigate a fascinating outcrop that caps the ridge,” reports Kristen Bennett, a planetary geologist at the USGS in Flagstaff, Arizona.Scientists have been characterizing the ridge-capping material, but also devoting time to use the Sample Analysis at Mars (SAM) Instrument Suite to look for methane.

MAHLI-Sol-2444-June-22-2019

“Curiosity Mars Hand Lens Imager (MAHLI) image produced on Sol 2444, June 22, 2019. Credit: NASA/JPL-Caltech/MSSS.” Larger image

  • Curiosity Mars Rover: Ridge Work – June.20.2019

    NASA’s Curiosity Mars rover is now carrying out Sol 2442 duties, parked on Teal Ridge, in the midst of an extended contact science campaign.At this ridge location, new imagery from the robot shows crossbedding in a bedrock layer, as well as a contact between the bedrock outcrop and a rubbly layer below.

Curiosity Navcam - Sol-2442-June-20-2019

A view from Teal Ridge taken by Curiosity’s Navcam – Sol-2442-June-20-2019

“Curiosity Navcam Left B image taken on Sol 2439, June 17, 2019. Credit: NASA/JPL-Caltech.” Larger image.

** Bob Zimmerman reports on interesting Mars images taken from orbit:

  • Strange Martian gullies – June.21.2019 – Bob finds the gullies in the image “Older Gullies and Channels” below fascinating –

    … because they appear to be some form of erosion drainage coming down both sides of a high ridge near the northern rim of this large apparently unnamed crater in the southern cratered highlands of Mars, to the west of Hellas Basin.On Earth my immediate explanation for this erosion would be a major monsoon-like storm, such as we get here in the southwest and call “gully-washers.” When a lot of water is quickly dumped onto a hill where there is not of vegetation to help bind the soil together, the water will quickly carve out gullies that looks almost exactly like these.

Older Gullies and Channels in Slopes of Softened Large Crater

Older Gullies and Channels in Slopes of Softened Large Crater – HiRISE

On Mars, who knows? It certainly wasn’t a monsoon thunderstorm that did this. And being in the Martian southern highlands it is unlikely it was from an ocean of any kind. Were there lakes here? Past research has found places where lakes might have existed on Mars, but these places are far north in the transitional zone into the northern lowlands.

  • Mass wasting on Mars – June.19.2019Mass wasting is a term that geologists use to describe a specific kind of avalanche, where the material moves down slope suddenly in a single mass.The image [below], taken from the image archive of the high resolution camera on Mars Reconnaissance Orbiter (MRO) and cropped and reduced in resolution to post here, shows a dramatic example of this kind of avalanche. You can see two separate avalanches, each of which moved a significant blob of material down slope into the center of the crater floor.

  • Wind and/or water erosion on the Martian northern lowlands – June.17.2019The picture [below], cropped and reduced in resolution to show here, was taken by the high resolution camera on Mars Reconnaissance Orbiter on April 21, 2019, and shows the erosion process produced by either wind or water as it flowed from the east to the west past one small mesa.It is almost certain that the erosion here was caused by wind, but as we don’t know when this happened, it could also be very old, and have occurred when this terrain was at the bottom of the theorized intermittent ocean that some believe once existed on these northern lowlands. The location itself, near the resurgences for Marineris Valles and the other drainages coming down from the giant volcanoes, might add weight to a water cause, except that the erosional flow went from east to west, and the resurgences were coming from the opposite direction, the west and the south.
Topographic Interactions in Vastitas Borealis

Topographic Interactions in Vastitas Borealis. HiRISE at U. of Arizona.

====

I Was a Teenage Space Reporter:
From Apollo 11 to Our Future in Space