Salt glaciers on Mercury?

From Figure A1 of paper
From Figure A1 of paper.

Based on a new analysis of data from the Messenger spacecrat that orbited Mercury from 2011 to 2015, scientists today posited the possibility that salt glaciers exist on Mercury and have reshaped its terrain in manner vaguely comparable to what Mars Reconnaissance Orbiter (MRO) has found on Mars.

You can read the paper here [pdf]. The image to the right, enhanced by the scientists to bring out the faint blue in the hollows, is remarkably reminiscent of the hollows and scallop terrain found in many places in the high Martian latitudes. From its conclusion:

Detecting widespread elemental volatile surface compositions, ubiquitous sublimation hollows, and extensive chaotic terrains has significantly reshaped our perception of Mercury’s geological past. These observations collectively point to the presence of volatile-rich strata spanning several kilometers in depth and likely formed before the [Late Heavy Bombardment] (∼3.8 billion years ago). This notion challenges the conventional view of a volatile-depleted Mercurian crust.

The morphologies within Mercury’s Raditladi basin bear a striking morphologic resemblance to glaciers on Earth and Mars, suggesting their origin from an impact-exposed [volatile-rich layer], likely containing halite. Our numerical simulations show that the unique rheological properties of halite, including the high thermal sensitivity of its viscosity, reinforce this hypothesis. These glacier-like features occur beyond the chaotic terrain boundaries, indicating a potentially global yet concealed, volatile-rich upper stratigraphy. We posit that the exposure of these volatile-rich materials, instigated by impact events, could have been instrumental in the formation and evolution of hollow features, signifying a complex geodynamic history of volatile migration and redistribution, essentially interconnecting some of the oldest and youngest stratigraphic materials on the planet.

The scientists do not have enough information as yet to determine if these glaciers are still active or not. Moreover, the theorized layer of volatile material near the surface remains unconfirmed, requiring in situ investigation to determine its existence with certainty. Like Mars, if it exists it likely only does so in the high latitudes.

BepiColumbo completes third Mercury flyby

Mercury as seen by BepiColumbo
Click for original image.

On June 19, 2023, the European Mercury orbiter BepiColumbo made the third of six planned flybys of Mercury on its way to orbit around that planet in 2025.

The closest approach was only 146 miles above the planet’s surface. Though no pictures were taken at that point because it was Mercury’s night side, as the spacecraft moved away it used one of its monitoring cameras, designed primarily to monitor the spacecraft itself, to look back at the planet. The picture to the right, cropped, reduced, and sharpened to post here, is one of the first taken. From its caption:

The image was taken at 19:49 UTC (21:49 CEST) by the Mercury Transfer Module’s monitoring camera 3, when the spacecraft was about 2536 km from the planet’s surface. Closest approach took place at 19:34 UT (21:34 CEST) on the night side of the planet at about 236 km altitude. The back of the Mercury Planetary Orbiter’s high-gain antenna and part of the spacecraft’s body is also visible in front of Mercury in this image.

Despite the dark nature of the image, several interesting geological features are seen in beautiful detail. Of particular interest is Beagle Rupes, a 600 km-long scarp that snakes over the surface. In this view it is seen cutting through a distinctive elongated crater named Sveinsdóttir, which likely got its shape from an impactor striking the surface at an angle.

The next flyby will occur on September 5, 2024.

Solar Orbiter captures Mercury crossing in front of the Sun

Solar Orbiter spots Mercury in front of the Sun
Click for full movie.

The European probe Solar Orbiter successfully filmed Mercury as it crossed in front of the Sun — from the spacecraft’s perspective — on January 3, 2023.

The transit was captured by several different instruments on Solar Orbiter, as shown at the link. The picture above is a screen capture from the short movie made by its Extreme Ultraviolet Imager. The black disk is Mercury, moving from the left to the right. In the background the limb of the Sun can be seen, with a distinct feature flaring out from that limb.

For Solar Orbiter, this particular transit offered a valuable chance to calibrate the instruments. “It is a certified black object travelling through your field of view,” says Daniel Müller, Solar Orbiter Project Scientist at ESA. Thus, any brightness recorded by the instrument within Mercury’s disc must be caused by the way the instrument transmits its light, called the point spread function. The better this is known, the better it can be removed. So be studying this event, the quality of the Solar Orbiter data can be ever further improved.

If the transit also produced some spectacular images, so much the better.

Changes on Mercury detected by Messenger over four year time period

Changes on Mercury seen by Messenger from 2011 to 2015

Using archival data collected from 2011 to 2015 while the orbiter Messenger circled Mercury, scientists have located twenty spots on the planet where something changed during that time period. The map to the right, adapted from the paper, indicates those locations. From the paper’s abstract:

We identified at least one change likely resulting from a newly formed impact crater with bright rays that extend away from the site. If all the changes result from impact events, then the present-day rate of impactors striking the innermost planet is 1,000 times higher than models predict. Therefore, we investigate other sources for these detected changes. We located several changes on steep slopes near tectonic landforms, consistent with ongoing tectonic activity. Additionally, we identified several changes in areas adjacent to hollow formations, consistent with present-day activity. These detected changes will be critical targets for the upcoming BepiColombo mission.

The data suggests several things. First, if the changes all come from impacts, than the number of asteroids in the inner part of the solar system where Mercury orbits the Sun is much higher than believed. Since it is very hard to observe asteroids there because of the Sun, this very well might be true.

Second, if the changes were not all caused by impacts, then they occurred either from earthquakes or the environmental extremes caused by daily and seasonal changes.

BeppiColombo’s first images of Mercury

Mercury by BebiColomo
Click for full image.

This past weekend the European/Japanese duel-orbiter mission made its first flyby of Mercury, taking its first images of that planet.

The photo to the right is one example, cropped and reduced slightly to post here. It was taken by the spacecraft’s monitoring cameras, designed for engineering purposes, which means the resolution is not very high and the camera is positioned so that parts of the spacecraft were visible in each shot. For example, the white strut in the lower right is the spacecraft’s magnetometer boom, which also was used to gather data during the flyby.

Still, the photos demonstrated that the spacecraft is pointing correctly and on course. It will complete five more Mercury fly-bys before going into orbit in 2025.

The next flyby will occur in June ’22.

BepiColombo about to make first of six Mercury flybys

The European/Japanese BepiColombo probe will make its first of six fly-bys of Mercury on October 1, 2021, as it steadily adjusts its flight path to enter orbit around the planet in 2025.

The mission is made up of two Mercury orbiters, Europe’s Mercury Planetary Orbiter and Japan’s Mio orbiter.

During the flybys it is not possible to take high-resolution imagery with the main science camera because it is shielded by the transfer module while the spacecraft is in cruise configuration. However, two of BepiColombo’s three monitoring cameras (MCAMs) will be taking photos from about five minutes after the time of close approach and up to four hours later. Because BepiColombo is arriving on the planet’s nightside, conditions are not ideal to take images directly at the closest approach, thus the closest image will be captured from a distance of about 1000 km.

The first image to be downlinked will be from about 30 minutes after closest approach, and is expected to be available for public release at around 08:00 CEST on Saturday morning. The close approach and subsequent images will be downlinked one by one during Saturday morning.

The cameras provide black-and-white snapshots in 1024 x 1024 pixel resolution, and are positioned on the Mercury Transfer Module such that they also capture the spacecraft’s solar arrays and antennas. As the spacecraft changes its orientation during the flyby, Mercury will be seen passing behind the spacecraft structural elements.

These will be the first close-up pictures of Mercury since the Messenger orbiter mission ended in 2015.

Two flybys of Venus set by two spacecraft on August 9th and 10th

Two European planetary probes, one launched to study the inner solar enviroment and the second to study Mercury, are going to fly past Venus only 33 hours apart on August 9th and 10th.

Solar Orbiter, a partnership between ESA and NASA, will fly by Venus on 9 August with a closest approach of 7995 km at 04:42 UTC. Throughout its mission it makes repeated gravity assist flybys of Venus to get closer to the Sun, and to change its orbital inclination, boosting it out of the ecliptic plane, to get the best – and first – views of the Sun’s poles.

BepiColombo, a partnership between ESA and JAXA, will fly by Venus at 13:48 UTC on 10 August at an altitude of just 550 km. BepiColombo is on its way to the mysterious innermost planet of the solar system, Mercury. It needs flybys of Earth, Venus and Mercury itself, together with the spacecraft’s solar electric propulsion system, to help steer into Mercury orbit against the immense gravitational pull of the Sun.

The two spacecraft will zip past a different side of Venus. For a variety of reasons, the imagery gathered will not of high resolution, though both spacecraft will gather data that will eventually be correlated with similar data being gathered by Japan’s Akatsuki probe, in orbit around Venus since 2015.

Mercury probe BepiColombo probe flies past Venus

Venus during BepiColombo fly-by
Click for full image.

The two-pronged European and Japanese probe BepiColombo today has completed its first of two fly-bys of Venus on its way to an arrival at Mercury in 2025.

The image to the right is one of 64 taken during the fly-by. The science team has created a movie from those images, showing Venus slide past as the spacecraft slewed to view it. During the fly-by the instruments on board its Japanese and European orbiters, both of which will separate and operate independently once they reach Mercury, gathered data of Earth’s sister planet.

The spacecraft still needs one more Venus fly-by plus six past Mercury to get it on a trajectory that will put it in orbit around Mercury. It has also already completed one fly-by past Earth in this complicated route.

BepiColumbo successfully completes Earth flyby

The Earth seen from BepiColumbo

BepiColumbo, the joint European-Japanese mission to Mercury, has successfully completed its fly-by of Earth.

The image to the right is one of the images of Earth it took during the fly-by. The white streak in the upper right is part of the spacecraft.

Mission scientists switched on a number of the duo’s instruments for the Earth pass, to test and calibrate them. Unfortunately, the main camera on Europe’s MPO couldn’t operate because of its position in the stack. But small inspection cameras to the side of Bepi did manage to grab some black & white pictures of the Earth and Moon.

The quote call’s the spacecraft a “duo” because it really is two orbiters presently latched together, the European Mercury Planetary Orbiter (MPO) and the Japanese Mercury Magnetospheric Orbiter (MMO). When it gets to Mercury these will separate.

Europe’s BepiColumbo mission to Mercury threatened by COVID-19

Because of the strict rules and work suspensions imposed due to the Wuhan virus panic, there will be a reduced workforce during the April 10, 2020 fly-by of Earth by the European Space Agency’s (ESA) BepiColumbo Mercury mission.

The press release tries to make it sound like they are heroically working through the fly-by, but the truth is revealed far down in the text:

The operation, however, will be performed with limited personnel at ESA’s European Space Operations Centre (ESOC) in Darmstadt, Germany, where engineers will have to comply with social distancing rules presently in place all over Europe as a response to the coronavirus pandemic. “The Earth swing-by is a phase where we need daily contact with the spacecraft,” says Elsa Montagnon, BepiColombo Spacecraft Operations Manager at ESA. “This is something that we cannot postpone. The spacecraft will swing by Earth independently in any case.”

The coronavirus threat forces the team to work with minimal face to face interaction while ensuring all steps in the process are properly covered. “During the critical two weeks prior to the closest approach, we need to upload safety commands to prepare the spacecraft for unexpected problems,” says Christoph Steiger, BepiColombo Deputy Spacecraft Operations Manager. “For example, we need to prepare the transfer module for the 34 minute-long eclipse when its solar panels will not be exposed to sunlight to prevent battery discharge.”

Operations can still be conducted as planned, he adds, but will require more effort and attention than in a normal situation. [emphasis mine]

I suspect that much of the software work is now being done remotely, but there is no doubt the inability to be present in the control room will prevent any quick fix, should the spacecraft need help during the fly-by.

Watch the Mercury transit of the Sun from home!

The November 11 transit of Mercury across the face the Sun will be live streamed by the Griffith Observatory in Los Angeles.

It appears that in Los Angeles the transit will have already started at sunrise, with Mercury at that point about a third of its way across the Sun’s face. Regardless, from about 7 am to 10 am (Pacific) the observatory will provide a view.

UPDATE: Images from an event in New Zealand will upload real time telescope images of the transit here.

How to safely watch the November 11 solar transit of Mercury

Link here. The last transit of the Sun by Mercury was in 2016, and the next won’t be until 2032.

The site emphasizes the most important fact: Do not watch this without the proper eye protection! If you fail to heed this warning you will likely go blind, for the rest of your life. However, if you follow the instructions and obtain the proper filters, you can watch most safely.

Mercury’s core is solid

By comparing computer models with data gathered during the closest orbits of the Messenger spacecraft when it was in orbit around Mercury scientists have concluded that the planet’s inner core is solid like the Earth’s, though much larger than the Earth’s relative to the planet’s size.

Genova and his team put data from MESSENGER into a sophisticated computer program that allowed them to adjust parameters and figure out what the interior composition of Mercury must be like to match the way it spins and the way the spacecraft accelerated around it. The results showed that for the best match, Mercury must have a large, solid inner core. They estimated that the solid, iron core is about 1,260 miles (2,000 kilometers) wide and makes up about half of Mercury’s entire core (about 2,440 miles, or nearly 4,000 kilometers, wide). In contrast, Earth’s solid core is about 1,500 miles (2,400 kilometers) across, taking up a little more than a third of this planet’s entire core.

BepiColombo begins first operational engine burn

The European/Japanese mission to Mercury has begun the first operational firing of its four ion engines, set to last for the next two months.

This might seem like a ridiculously long burn, since most conventional rocket engines fire for minutes, not months. These are ion engines, however, far more efficient but producing a very tiny acceleration. It takes a long time for their burns to accumulate a velocity change.

BepiColombo tests its ion engines

The joint European/Japanese mission BepiColombo has begun testing its ion engine thrusters for the first time in space as it heads to Mercury.

Testing took place during a unique window, in which BepiColombo remained in continuous view of ground-based antennas and communications between the spacecraft and those controlling it could be constantly maintained. This was the only chance to check in detail the functioning of this fundamental part of the spacecraft, as when routine firing begins in mid-December, the position of the spacecraft will mean its antennas will not be pointing at Earth, making it less visible to operators at mission control.

They have so far successfully tested two of the four engines.

Ariane 5 launches BepiColumbo to Mercury

An Arianespace Ariane 5 rocket successfully launched the joint European/Japanese BepiColumbo mission to Mercury this weekend.

BepiColombo consists of two orbiters: Japan’s Mercury Magnetospheric Orbiter (MMO) and ESA’s Mercury Planetary Orbiter (MPO), both of which will be carried together by the Mercury Transport Module (MTM).

While MPO will go into an approximately 400 x 1500 km mapping orbit around Mercury, MMO will enter a highly elliptical orbit to study the planet’s enigmatically strong magnetic field.

The leaders in the 2018 launch race:

28 China
17 SpaceX
8 Russia
8 ULA
7 Europe (Arianespace)

China still leads the U.S. in the national rankings 28 to 26.

Betty Grissom, widow of Mercury astronaut Gus Grissom, passes away

R.I.P. Betty Grissom, the widow of Mercury astronaut Gus Grissom, who died in the Apollo 1 launchpad fire in 1967, passed away today at 91 after a sudden illness.

The article makes a big deal about her successful lawsuit against North American Rockwell, the manufacturer of the Apollo capsule. I think we should instead emphasize her own courage, allowing her to agree and support her husband as he risked and lost all to help the United States win the race to the Moon.

The thin dense crust of Mercury

Using data gathered by the MESSENGER spacecraft while it was in orbit around Mercury, scientists now estimate that the planet’s crust is thinner than previously believed, 16 miles thick rather than 22 miles.

The crust is also as dense as aluminum. It is also the thinnest crust, relative to the planet’s core, of any rocky planet in the solar system.

Mercury’s core is believed to occupy 60 percent of the planet’s entire volume. For comparison, Earth’s core takes up roughly 15 percent of its volume. Why is Mercury’s core so large?

“Maybe it formed closer to a normal planet and maybe a lot of the crust and mantle got stripped away by giant impacts,” Sori said. “Another idea is that maybe, when you’re forming so close to the sun, the solar winds blow away a lot of the rock and you get a large core size very early on. There’s not an answer that everyone agrees to yet.”

There appears to be a great deal of uncertainty to these conclusions, and I would not be surprised if these conclusions change with the arrival of more data.

ESA unveils dual orbiter mission to Mercury

After twenty years of development, the European Space Agency this week finally unveiled the completed dual orbiters that it hopes to launch on a seven year journey to Mercury in October 2018.

The 4,100-kilogram BepiColombo consists of two orbiters that will launch together — the ESA-managed Mercury Planetary Orbiter (MPO) and the JAXA-owned Mercury Magnetospheric Orbiter (MMO). The two spacecraft will be delivered to the orbit around Mercury stacked on top of each other by the Mercury Transfer Module (MTM). During the seven-year journey, the MMO will be shielded from the sun by the MMO Sunshield and Interface Structure (MOSIF), which will also serve as a mechanical and electrical interface between the two orbiters.

“MPO focuses on the planet, the surface and the interior size,” said Reininghous. “The orbit is a polar one — 480km times approximately 1500km — a little bit elliptical but extremely close to the planet as such with a return period of 2.3 hours. The data return is estimated at 1.5 gigabit per year.”

The MMO will focus on the planetary environment including the planet’s atmosphere, according to Reininghous. “The orbit is also polar but far more elliptical — 590 km times approximately 11,700 km. It has a period of 9.3 hours. The data return is approximately 10 percent of what we expect from the MPO.”

The European orbiter is much larger and more expensive, with Japanese probe budget being about a tenth the cost.

According to ESA, the mission took so long to build because in 2004, after about seven years of development, ESA suddenly realized that its orbiter’s thermal protection was inadequate, and required a complete redesign. To me, this is either outright incompetence (they knew from the start they were going to Mercury) or a clever way to extend the funding so that it provides an entire lifetime’s work for its builders. Think about it. Twenty-one years from concept to launch, then seven years to fly to Mercury, and then one to two years in orbit. That’s more than thirty years for this single mission.

Mercury’s transit today

Here are a few links on today’s transit of the Sun by Mercury, which is going on right now.

I could give more, but this event is hardly as important as many new media are saying. It is interesting, and rare, and important in that it helps scientists get a better understanding of the uncertainties in their exoplanet research, but hardly important scientifically.

Consider this however: Mercury’s real orbit has it circle the sun every 88 days. If we could only detect it by the transits seen from Earth, we would only see it cross the Sun in 2006, 2016, 2019, and 2032. Figuring out its real orbit from that data would likely be impossible. Now, I realize that these seemingly random transits are partly determined by the Earth’s own orbit around the Sun, but they still illustrate that our use of transits to detect and characterize exoplanets has its limits. And in science one must always be aware of one’s limits.

Global elevation map of Mercury

The science team for Messenger have now released a new digital elevation model of Mercury’s global surface.

The new product reveals a variety of interesting topographic features, as shown in the animation above, including the highest and lowest points on the planet. The highest elevation on Mercury is at 4.48 kilometers [2.78 miles] above Mercury’s average elevation, located just south of the equator in some of Mercury’s oldest terrain. The lowest elevation, at 5.38 kilometers [3.34 miles] below Mercury’s average, is found on the floor of Rachmaninoff basin, a basin suspected to host some of the most recent volcanic deposits on the planet.

If you watch the animation at the link, you will notice that the high points tend to cluster in the lower latitudes, while the low points tend to favor the high latitudes, suggesting a very slightly bulged shape, which is not surprising considering Mercury’s close proximity to the Sun.

The data release today also included an additional map showing the known geological features in more detail.

New results from Messenger at Mercury

Hollows on Mercury

As Messenger nears the end of its lifespan orbiting Mercury, the project scientists have put together a slate of talks on what they have learned, presented today at the 46th annual Lunar and Planetary Science Conference in Houston.

The images that go with these presentations can be found here.

The image on the right is a close-up of the mysterious and unexpected hollows that Messenger found scattered everywhere on Mercury’s surface. According to today’s presentation, scientists now believe they are very recent features, formed when material with a lower boiling point evaporated away because of Mercury’s harsh and very hot environment. Imagine for example a vein of dry ice in a rock crack. The temperature rises above freezing and the dry ice evaporates. And like the convection bubbles in tomato sauce as it simmers, some of that evaporation pushes its way up by popping out a bubble and leaving behind a hollow.

In the case of Mercury the material is likely not dry ice, though scientists as yet are unsure what it is.

They are also presenting talks on magnesium on Mercury, the planet’s many scarps, and detailed observations of the permanently shadowed polar craters that might have water-ice in them.

Ice photographed in Mercury’s permanently shadowed craters?

Kandinsky Crater on Mercury

Using Messenger, scientists think they have obtained optical images of the ice that is thought to exist in the permanently shadowed craters of Mercury.

Although the polar deposits are in permanent shadow, through many refinements in the imaging, the WAC [Messenger’s camera] was able to obtain images of the surfaces of the deposits by leveraging very low levels of light scattered from illuminated crater walls. “It worked in spectacular fashion,” said Chabot.

The team zeroed in on Prokofiev, the largest crater in Mercury’s north polar region found to host radar-bright material. “Those images show extensive regions with distinctive reflectance properties,” Chabot said. “A location interpreted as hosting widespread surface water ice exhibits a cratered texture indicating that the ice was emplaced more recently than any of the underlying craters.” In other areas, water ice is present, she said, “but it is covered by a thin layer of dark material inferred to consist of frozen organic-rich compounds.” In the images of those areas, the dark deposits display sharp boundaries. “This result was a little surprising, because sharp boundaries indicate that the volatile deposits at Mercury’s poles are geologically young, relative to the time scale for lateral mixing by impacts,” said Chabot. [emphasis mine]

The image on the right is of the crater Kandinsky, and shows a very intriguing bright area on the crater’s central peak.

I highlighted that one word in the the scientist’s quote above to emphasize how preliminary these conclusions are. The images are intriguing, but I would not at this time bet a lot of money on these conclusions. Ice might be the best explanation for this data, at this time, but I would not be surprised at all if later research finds this conclusion to be false.

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