SOLAR SYSTEM

SOLAR SYSTEM NEWS

A Case Study on How Not to Conduct Science

NASA and other Federal science programs are under severe attack, as described in earlier sections of A+StW above, but alas, Science is also under attack from an Enemy Within: Harvard’s gadfly pseudoscientist and shameless self-promoter, Avi Loeb. Real scientists adhere to the well-known and successful process of scientific inquiry; phonies selectively seek (and distort) evidence to support their preconceived notions. Some are obvious quacks, like Percival Lowell and Erich van Däniken, but a bozo like Loeb, who has a major title and Ivy League affiliation, can cause real damage.

The issue at hand is the approach of the third object known to have come from completely outside the Solar System, 3I/ATLAS, a seven-mile-wide asteroid-type body. There is no question that is coming in from beyond the Sun’s gravitational influence, making it an object of great legitimate scientific interest. But Loeb and company immediately proclaimed, with a high degree of unjustified certainty, that this object is a device/artifact of alien manufacture, channeling Science Fiction writer Arthur C. Clarke’s interesting story, the “Rendezvous with Rama.” Again. He pulled the same publicity stunt when the first extra-solar object appeared, 1I/’Oumuamua. He believes that there is indisputable evidence of alien technology here on Earth, and is trying to find it, giving breathless accounts of tiny bits of metal on the ocean floor and other things that have many other more-plausible explanations. “I wouldn’t have seen it if I hadn’t believed it” is not the way Science operates! Now he’s agitating to make NASA redirect the Juno spacecraft, presently orbiting Jupiter returning valuable data, to make a sorta-close pass to find out more about it, something that it lacks the fuel to accomplish.

The general public eats this stuff up. Surf around, and you’ll find a lot of click-bait items that assume Loeb is correct and NASA’s inaction is somehow sinister, but almost none about the scientific importance of this object. IMO this is really bad, because it is just another way that the line between real Science and pseudoscience is blurred in the mind of the public. It’s bad enough that outlets like the History Channel and the Discovery Channel will run science pieces from NASA and NSF, book-ended by shows breathlessly expounding Alien bodies, UFO “proof,” ghost chasing, and the Bermuda Triangle.

Even a reputable outlet can be (semi) fooled. A recent item on the Aviation Week website factually describes the discovery and trajectory of 3I/ATLAS, and Loeb’s scheme to (ab)use Juno, but fails to mention Loeb and his promotion of his Rama hypothesis.

Arthur C. Clarke’s estate should sue Loeb (and Harvard) for plagiarism!

Another example of Loeb’s bas-ackwards approach to scientific inquiry is his hypothesis that Mars had a highly-advanced technological civilization in the distant past that went belly-up, with all evidence of it obliterated by subsequent impact cratering. Prove me wrong, he says, ignoring that the burden of proof is on him to prove himself right.

Scientists can put forward an “out there” hypothesis in a legitimate manner. David McKay, a scientist at NASA’s Johnson Space Center, and others, published a paper in 1996 in the prestigious peer-reviewed journal, Science, that suggested that meteorite ALH84001 contained evidence of microbial life from the distant past (McKay, D. S., E. K. Gibson, Jr., K. L. Thomas-Keprta, H. Vali, C. S. Romanek, S. J. Clemett, X. D. F. Chillier, C. R. Maechling, and R. N. Zare. 1996. Search for past life on Mars: possible relic biogenic activity in Martian meteorite ALH84001. Science 273:924–930). They cited four lines of evidence and were straight-up about the strength/weakness of each. All four had plausible alternative explanations, but the authors used a “common denominator” approach to their conclusion.

As Carl Sagan once said, “Extraordinary Claims Require Extraordinary Evidence (to be believed).” The ALH84001 evidence was intriguing, but not extraordinary enough to be adopted.

Sometimes evidence so extraordinary comes along to compel almost-unanimous acceptance. One example is the recognition that some meteorites found on Earth actually did originate on Mars, see: https://triage19.com/products/REV/REV036C06.pdf especially Figure 2. Another is the evidence that led to the adoption of Plate Tectonics model of Earth’s crust; see the “History of the theory” section here: https://en.wikipedia.org/wiki/Plate_tectonics.

Loeb’s Rama hypothesis is neither intriguing nor compelling; it is wishful thinking and shameless self-promotion. I’ll leave it for the critique by Professor Steve Desch, Arizona State University astrophysicist, writing in Medium.com; see: https://medium.com/p/34268f892ba8.

The Chinese are laughing at us.

As long as I’m on my soapbox, see the first piece in the Education News section below. It’s about Pluto’s change in status and how that is an excellent example of how the process of scientific inquiry operates.

New Perseverance Panorama: NASA released a new panorama of Mars on August 6, that shows the amazing terrain of the site they named “Fallbreen.” It shows flat rocks, rippled sand, a contact between geologic units, and most intriguingly, a rock that appears to lie atop a sand ripple, and the site where Percy took a rock sample. See it in full detail at: https://www.jpl.nasa.gov/news/nasas-perseverance-rover-captures-mars-vista-as-clear-as-day.

Lunar Trailblazer Spacecraft Fails:The small satellite was to map lunar water, but operators lost contact with the spacecraft the day after launch and were unable to recover the mission. Find out about the mission and what went wrong at: https://www.nasa.gov/missions/small-satellite-missions/lunar-trailblazer/nasas-lunar-trailblazer-moon-mission-ends and https://www.jpl.nasa.gov/news/nasas-lunar-trailblazer-moon-mission-ends.

SOLAR SYSTEM FYI

Venus Tectonism: Magellan Data Revisited: Data analysis from a NASA mission often provides important information long after the mission has ended. Such was the case recently for the Magellan mission to Venus back in the 1990’s. It carried a radar mapper that could image surface features through Venus’ cloudy atmosphere. Venus’ surface is marked by odd circular structures known as “coronae,” thought to be a manifestation of volcanism. New analysis of many coronae show that they likely have a mantle plume beneath them, like Iceland does on Earth. But Magellan was thirty years ago, and present-day radar systems are much more sensitive and thereby more capable of ascertaining more details of these enigmatic structures and the fracture patterns around them. Such a radar system is slated to be onboard the VERITAS Discovery mission, which was to be launched in the early 2030s. Alas, if the present 2025 NASA budget is cut as much as it appears it will be, VERITAS will be canceled.

Venus is almost identical to Earth in size and composition, yet the surface conditions on Venus are much more hellish than expected due on to Venus being closer to the Sun. “Why is Venus so inhospitable, and could Earth end up that way?” are the two most important questions facing planetologists today. VERITAS and DAVINCI, another approved Discovery-class mission, would have provided a LOT of data that would help scientists understand planetary evolution, and Humanity’s possible future, more clearly.

Another Dwarf Planet Discovered: An enormous quantity of observational data floods our analysis capability, but the occasional nugget of info found within can really prove worthwhile. One such is the Solar System’s latest dwarf planet to be discovered, provisionally-named 2017 OF₂₀₁. It is about 400 miles in diameter and is in a highly-elliptical, very-large orbit, with an orbital period on the order of 25,000 years. Its perihelion is 44.9 AU and its orbit extends into the inner Oort Cloud, too distant to have been responsible for observed planetary perturbations – it’s not Planet X. For more on this most recent addition to the Sun’s extended family, see: https://skyandtelescope.org/astronomy-news/another-dwarf-planet-in-our-solar-system.

Crater Ejecta, a Clue to the Subsurface: The detailed study of impact craters has long been used to determine the properties of impacts and the surface upon which they occur, and the population of craters can provide clues to the absolute age of the surface on which craters are found. Recent research shows that not only the crater itself can be revealing, the spread of material ejected by the crater’s formation can, too. In a nutshell, an impact into a solid rock surface distributes ejecta much more broadly than an impact into a mix of regolith and ice. For more information on this investigative tool, see: https://www.sciencedaily.com/releases/2025/05/250514175436.htm \.

Large Organic Molecules on Mars: NASA’s two active rover mission on Mars, Curiosity and Perseverance, were sent to areas where geologic evidence indicated the presence of large amounts of surface water in the distant martian past. One of the things they are looking for is pre-biotic chemistry, such as complex organic molecules (remember, “organic” means “containing carbon,” not “biological material.”) Curiosity recently scored big with the discovery of three types of organic molecules: decane, undecane, and dodecane, having 10, 11, and 12 carbon atoms in a chain, respectively. The molecules are likely fragments of fatty acids, which are part of the set of chemical building blocks of life here on Earth. For more information on this story, see: https://science.nasa.gov/missions/mars-science-laboratory/nasas-curiosity-rover-detects-largest-organic-molecules-found-on-mars

Is Mars’ Core Fully Molten? Mars has no appreciable planetary magnetic field now, but there is significant geological evidence that it once had a strong magnetic field in the past. The issue is important for Mars’ evolutionary history, because a magnetic field there would have inhibited the stripping of gases from Mars’ atmosphere by the solar wind, making surface conditions more conducive to life. But the remnant features of Mars’ past field have a strange property; they only a present in Mars’ southern hemisphere. Computer models of a Mars with a solid inner core and a not-solid outer core (like Earth) show the resulting field should be symmetrical. However, when a fully-liquid core is considered, those same models show that a one-hemisphere-only field is possible. The new look was triggered by data from NASA’s InSight lander, which showed that Mars’ core was made of lighter elements than expected. For more on this research, see: https://www.sciencedaily.com/releases/2025/04/250415143516.htm.

What Makes Mars So Red? There is overwhelmingly-abundant evidence that Mars had a lot of surface water in the distant past, and we’ve also known for some time that iron oxides are responsible for Mars’ distinctive reddish color. But “iron oxides” cover a wide range of molecules, several of which are present in martian dust. One possible candidate is hematite (its very name is derived from “blood” in Latin); it forms in the presence of very hot water. But recent research results indicate that an iron oxide called “ferrihydrite” is most responsible for the redness of Mars. This is significant because ferrihydrite can form in cool water, at temperatures conducive to biological activity! The present martian surface environment is pretty hostile to life as we know it, but that was likely not true in the past. The same processes that led to life on Earth could well have worked on Mars, a finding of tremendous scientific, philosophical, and religious consequence. For a summary of this research, see here; for the paper published in Nature Communications, see here: https://www.nature.com/articles/s41467-025-56970-z. The Sky & Telescope website also had a good summary, see: https://skyandtelescope.org/astronomy-news/why-is-mars-red.

Callisto is an Ocean World (?): We are confident that some of the icy bodies in the Solar System have a thick liquid ocean surface, overlain by a thick cover of ice. Jupiter’s Europa and Saturn’s Enceladus are prime candidates, but some of the other moons and perhaps Pluto may have enough interior tidal heating that they differentiated enough to have a thick, iced-over surface, too. Jupiter’s Callisto is the latest to be found to have evidence of a sub-surface liquid ocean, based on repeated observations of its magnetic field and ionosphere acquired during eight close passes by the Galileo spacecraft. For more info in this intriguing possibility, see: https://eos.org/research-spotlights/jupiters-moon-callisto-is-very-likely-an-ocean-world.

BepiColumbo at Mercury: Only two spacecraft have explored Mercury significantly to date: NASA’s Mariner 10, which flew by three times in the early-mid 1970s, and MESSENGER, a successful orbital mission that ended in 2015. ESA’s BepiColumbo mission was designed as a follow-up, launching in October, 2018. Moving inward in the Solar System takes a lot of energy, just like moving outward does, and NASA trajectory planners use gravity assists to move inward economically. Six gravity assists were necessary to get BepiColumbo ready for final orbital insertion via rocket in November, 2026. The first assist was from the Earth, the next two were from Venus, and three were required at Mercury, the last of which was last week. It showed the south polar region of Mercury in better detail than ever before. For more info about the mission, see: https://sci.esa.int/web/bepicolombo; for more about this third fly-by, see: https://skyandtelescope.org/astronomy-blogs/astronomy-space-david-dickinson/bepicolombo-mission-returns-to-mercury-for-best-flyby-views-yet.

Pluto and Charon: Kiss and Capture? Why does Pluto have such a large moon, relative to its own size? A new mechanism of the Pluto/Chiron system’s formation is that two icy bodies collided in the outer Solar System, but with rather low relative speeds, with the consequence that they glommed onto one another rather than destroyed each other (as was the case when the proto-Earth was hit by another body), spinning like a demented snowman. Eventually the two pulled apart, leaving a scar that today forms part of Pluto’s “Heart” (Sputnik Planitia), a scenario supported by recent computer modeling. For a summary of this work, see: https://phys.org/news/2025-01-newly-capture-mechanism-formation-pluto.html

Pluto and Charon: Large Impact Mascon? An alternative process for the creation of Sputnik Planitia is that it is a mega-impact feature the filled with a slab of “excess” mass – water ice, which is heavier than nitrogen ice prevalent there. See the proposed explanation in more detail here: https://skyandtelescope.org/astronomy-news/sputnik-planitia-drives-plutos-wandering-heart.

2060 Chiron is a Unique Hybrid: Chiron is a member of a class of bodies called “Centaurs.” Just as a centaur is a man/horse hybrid in mythology, Centaurs have characteristics of both asteroids and comets in reality, and their orbits are confined to the belt between Jupiter and Neptune. Detailed observations from the JWST show the presence of CO2 and CO ice on Chiron’s surface and CO2 and CH4 in its comet-like coma, a shroud of gas and dust released from Chiron. CO2 and CH4 ices have also been detected on some Trans-Neptunian Objects. Chiron was discovered in 1977, and has been observed in more detail than the other Centaurs. Trans-Neptunian Objects tend not to have a coma, because they are so far from the Sun that their surface ice cannot sublimate. Classical asteroids have no surface ices. Centaurs do have surface ices, but sublimation is limited to those times when they are closer to the Sun. The details of the chemistry of ices and gases has implications for the evolution of the Solar System. For a summary of this work and its implications, see: https://www.sciencedaily.com/releases/2024/12/241218131526.htm; for the paper in Nature Geoscience, see: https://www.nature.com/articles/s41561-024-01612-0.

Chiron isn’t the only Centaur of Note! We’ve all seen some amazing pictures of the deepest of deep-space objects acquired by the JWST. Numerous objects now bear (perhaps temporary) labels as the “most distant known.” But the JWST makes important observations much closer to home, too!

Chiron is the oddest Centaur (see news above), but the largest Centaur asteroid is 10199 Chariklo, discovered in 1997 and named for the wife of the centaur Chiron and (perhaps) a daughter of Apollo.

Recall how the rings of Uranus were discovered – it’s a classic case of learning things by looking at them in front of other things. Astronomer James Elliot, aboard the Kuiper Airborne Observatory, was measuring the brightness of a background star as Uranus passed in front of it, hoping to gain information about the uranian atmosphere (a la Mariner 4 at Mars). Just prior to the occultation, Elliot and his team saw the light from the background star dim slightly five times, and then they saw the same thing just after the star was occulted. Elliot knew those dips were caused by Uranus’ hitherto unknown ring system!

Well, the same thing happened in 2013 with Chariklo. Astronomers calculated that Chariklo would pass in front of a minor star, and they wanted to observe that occultation closely from many locations on Earth in order to be able to refine estimates of Chariklo’s size and shape. Those observations went well but were overshadowed (sorry) by a scene straight out of Jim Elliot’s experience.

Seven seconds before the occultation would begin, astronomers saw two small dips in the star’s light, and another two seven seconds after the occultation. Rings!

Finding rings around one of the Sun’s larger planets was a wonderful accomplishment, but rings around an asteroid?!?

Chariklo was in the news again recently. The JWST was able to see it occult star named Gaia DR3 6873519665992128512, the first time it had observed any occultation event and a portent of JWST’s ability to “do science” much closer to home than the very-distant objects it was built to study.

The leading hypothesis so far as to why an asteroid could have rings are that the rings are remnants of a larger debris field created by an impact with another icy body. For more info an Chariklo and the JWST, see here: https://phys.org/news/2023-01-webb-spies-chariklo-high-precision-technique.html.

Enceledus’ Thermal Vents: Several lines of evidence indicate that Saturn’s moon, Enceladus, has a deep iced-over ocean with the chemistry potentially amenable to biological activity. The same sort of gravitational/tidal tug-of-war that makes Jupiter’s moon, Io, so volcanically active keeps the ocean liquid, and causes geyser-like spewing from fractures in the ice cover. We know about the tides, and about the chemistry of the spray from the fractures because the Cassini spacecraft was steered thorough! The situation on Jupiter’s moon, Europa, is almost certainly similar; investigating it further is the purpose of the recently-launched Europa Clipper spacecraft. But we know that there is interesting chemistry at Enceladus, so further exploration is needed there, too. One way to do so is to study further such hydrothermal vents and the environment they create in their vicinities. We’ve known about the vents and the life they support on Earth for some time now, but work is ongoing, and we are learning more all the time in preparation for the next step, direct exploration is needed; see: https://eos.org/articles/arctic-hydrothermal-vents-may-resemble-those-on-enceladus. And under development….

NASA’s Swimming Robots: Jupiter’s Europa and Saturn’s Enceladus almost certainly have large-scale oceans, iced over, but still liquid. Ganymede and Callisto, Mimas, and some of the bodies in the outer Solar System likely do, too. We know that Enceladus has active hot spring activity that could keep its ocean liquid, because the Cassini spacecraft was able to sample the plume of one of its large geysers. Everywhere on Earth oceanographers have been able to find deep-water hot springs, they’ve found abundant life. The likelihood that such conditions elsewhere might also support abundant life makes exploring those ice-covered extraterrestrial oceans a high priority. The Europa Clipper spacecraft, presently en route to Jupiter, is designed to examine Europa more closely, but what would really be useful would be to get a remotely-controlled submersible to ply those dark and deep seas, so far away. And that is just what NASA is planning to do!

NASA is experimenting with small submersible prototypes that could be delivered to a subsurface ocean, carried through the ice by a lander with a heat source that allows it to melt its way through the ice crust above. See: https://www.jpl.nasa.gov/news/nasa-ocean-world-explorers-have-to-swim-before-they-can-fly for more information (when the JPL News site is working). And, …

Enceladus May Someday Have EELS! The Planetary Society has produced a radio program about a concept to explore the subsurface ocean of Enceladus. The concept is called the “Exobiology Extant Life Surveyor” (EELS). The acronym is particularly apt, because EELS would be a snake-like, AI-enabled robot capable of navigating the surface fractures of Enceladus and accessing the liquid ocean at depth. Check out the radio program info here: https://www.planetary.org/planetary-radio/2024-eels and the JPL webpage about the EELS concept here: https://www.jpl.nasa.gov/robotics-at-jpl/eels! But wait, there’s more!

MARS

Active Processes on Mars: One of the most exciting observations of Mars made by the Mariner 9 orbiter was the presence of surface features that changed with time. Several ideas for them had been proposed, but it quickly became apparent that the changes were caused by dust and the thin martian winds. Studies of wind-related sand/dust movement on Earth followed, to help better understand such things on both planets. Craters, mountains, and other topography and the wind can make specific erosion patterns. Having an obstacle of known size and shape cause redistribution of surface materials would help. And the now-retired InSight lander is serving science one more time. Images acquired by the HiRISE camera aboard the Mars Reconnaissance Orbiter show a pattern of dust erosion around the lander that allow scientists to estimate the deposition and erosion of dust under observable weather conditions. For more on this study, see: https://www.jpl.nasa.gov/news/nasa-mars-orbiter-spots-retired-insight-lander-to-study-dust-movement.

Springtime on (Boom!) Mars: Mars has seasons like the Earth does, but they all last much longer because of Mars’ longer year. Mars has polar caps like Earth does, too, but they are made of both frozen CO2 and H20. Both ices sublimate (turn from solid to gas without a liquid phase in between), and if gaseous CO2 builds up beneath and H20 ice layer, an explosion can occur, making distinctive surface features. For more on this unusual surface process, see: https://www.jpl.nasa.gov/news/avalanches-icy-explosions-and-dunes-nasa-is-tracking-new-year-on-mars!

Perseverance Reaches the Top of Jezero Crater! Percy reached “Lookout Hill” on the rim of Jezero Crater recently. It had originally landed on the crater’s floor, and one of its primary missions was to make a detailed examination of a delta built within Jezero when the crater was partially-filled with water, in the distant martian past. It has completed the delta operations, exploring the “fan front,” “upper fan,” and “margin unit.” It’s now on its fifth campaign, the “Northern Rim.” Until now, Percy had been exploring terrain that post-dated the emplacement of Jezero Crater. Now that it is starting to drive away from the rim, Percy will begin to encounter formerly-deep-seated rocks ejected by the formation of Jezero, and rocks that were there when Jezero was formed. Additional exploring may get Percy to large ejecta blocks from the formation of the Isidis Basin. For more on these exciting results, and for a couple of cool NASA YouTube videos of Percy’s travels, see: https://www.nasa.gov/missions/mars-2020-perseverance/perseverance-rover/nasas-perseverance-rover-reaches-top-of-jezero-crater-rim.

Mars: CO2 Polar Caps and Icy Rivers Beneath? An interesting hypothesis has been proposed by Peter Buhler of the Planetary Science Institute regarding the evolution of Mars’ climate and the appearance of many landforms indicative of water flow at a time when Mars’ atmospheric pressure was too low to allow it. In a nutshell, the climate became cool enough for the CO2 in Mars’ atmosphere to freeze out, covering the surface with a thick layer of insulative dry ice. Thermal heat from Mars’ interior was enough to melt any water ice present and allow it to flow beneath the dry ice “glacier.” For more on this interesting idea, see: https://skyandtelescope.org/astronomy-news/solar-system/icy-rivers-may-have-flowed-on-ancient-mars.

Bennu is Shedding; NASA Style; and How “Science” Operates: The line between “asteroid” and “comet” has been blurred significantly by recent discoveries.Decades ago, solar system astronomers discovered that an asteroid (Phaeton), not a comet, was the source of the Geminid meteor shower. As a consequence, some would come to refer to it as a “rock comet” (Somewhere Bill Haley is smiling!). Then, in early 2019, the OSIRIS-REx spacecraft, then in orbit around asteroid Bennu showed that it was shedding considerable material, albeit at a low rate.

But are asteroids (and comets) the only source of debris in the inner Solar System?

A few months ago, authors of a paper published in JGR: Planets make the case that the very small particles responsible for the Zodiacal Light (the “False Dawn” of Omar Khayyam) actually come from either Mars or its two tiny moons (or perhaps martian moon(s) no long in existence). The data upon which that conclusion was based came primarily from the analysis of micro-meteoroid impacts on the solar panels of the Juno spacecraft when it was en route to Jupiter!

Longtime A+StW fans know that I frequently cite NASA’s know-how, and how they not only do the extremely difficult, they do it with style. The radio science experiment aboard Mariner 4 was one case in point; the item above is another example. Not only is Juno actively returning data and accomplishing its mission objectives, creative scientists have figured out a way to squeeze very interesting information from an unanticipated source!

Here’s another example of how the process of scientific inquiry works, too. The data from Juno’s micrometeoroid hits very strongly suggest the Mars system is the source of the impactors. However, neither the researchers or other planetary scientists have come up with a mechanism that would remove material from Mars, Phobos, or Deimos and get it into the interplanetary medium to cause the ZL. But the observational data will now drive more investigation, and Science will march on!

We had a similar situation when the first identification of the martian origin of some of the meteorites on Earth was announced. The observational data were overwhelming, but nobody thought impact could remove material from Earth’s gravity field, that is, until the data spurred them to investigate further.

Remember, this thing we call “Science” in not just a body of accumulated knowledge, it’s more importantly the process through which that knowledge was acquired!

For more info, see:

Summary of Bennu activity: https://eos.org/editors-vox/up-close-with-an-active-asteroid

JGR Planets paper: https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020JE006381

Mimas Joins the “Moons with Subsurface Oceans Club!” Wow! When planetary scientists first saw close-up images of Jupiter’s moon, Europa, and Saturn’s moon, Enceladus, they were deeply suspicious that both had a deep, liquid ocean with a thick ice cover. That proved to be correct, with the reason for them having an underground ocean was the same tidal heating mechanism proposed for Jupiter’s moon, Io, which was proven so dramatically when Voyager 1 fly by it (see more of that story here). Subsequent studies have shown that two of Jupiter’s other large moons, Ganymede and Callisto, also have large underground bodies of liquid (mostly) water. Saturn’s large moons, Titan and Enceladus do, too. The Cassini spacecraft even flew through plumes of water spewing from cracks on the surface of the latter (and found chemistry akin to that of “black smoker” hot springs in deep ocean locales on Earth – which by the way teem with life). And there is strong evidence that dwarf planets Ceres and Pluto; Neptune’s large moon, Triton; and several of the moons of Uranus have them, too. All these bodies make quite a club!

A moon doesn’t have to be big to have enough internal heating from tidal forces to make an underground ocean (but it helps). It turns out that a small moon can, too, provided it’s close enough to larger bodies to be subject to sufficient tidal stresses. Planetologists analyzing the motion of Mimas, a small but close-in moon of Saturn, also has underground liquid water. [Mimas was noteworthy when the first up-close pictures of it were acquired, because it has one giant crater that makes it a dead ringer for Star Wars’ Death Star, which was fresh on everyone’s mind when the fly-by took place.]

But wait, there’s more! Detailed tracking of the Cassini spacecraft provides data that indicates that the subsurface ocean on Mimas is very, very young, geologically speaking, only a few million years old.

For more on Mimas and its hidden ocean, see: https://www.sciencedaily.com/releases/2024/02/240207120512.htm and https://www.astronomy.com/science/evidence-grows-for-a-young-ocean-lurking-under-mimas-icy-crust

Uranian Moons Harbor Subsurface Oceans: Mimas, Europa, and Enceladus aren’t the only outer planet moons with a subsurface ocean! The National Academy’s 2023 Planetary Science and Astrobiology Decadal Survey identified the further exploration of Uranus and its larger moons as a priority goal. NASA has only visited Uranus once before, a fly-by by the Voyager 2 spacecraft in January, 1986 (the excitement the real-time release of the images of the fly-by is related here). The need for information to assist planning the recommended mission led scientists to revisit the 37-year-old data. Computer modeling not possible back then shows that the four largest moons (Ariel, Umbriel, Titania, and Oberon) are large enough to have Uranus’ gravity generate internal tidal heating that could lead to their having a subsurface ocean of liquid, likely water. This is the same mechanism driving internal geologic processes on Jupiter’s large satellites and Saturn’s Titan. For more information on this study, see: https://www.jpl.nasa.gov/news/new-study-of-uranus-large-moons-shows-4-may-hold-water.

SOLAR SYSTEM LINKS AND OTHER INFORMATION

Mars Odyssey

https://mars.nasa.gov/odyssey

https://mars.nasa.gov/odyssey/files/odyssey/Odyssey0302.pdf

https://themis.asu.edu

Mars Express

https://sci.esa.int/web/mars-express/-/31021-summary

https://sci.esa.int/web/mars-express/-/55263-beagle-2-lander-found-on-mars

Mars Science Laboratory (aka Curiosity)

https://mars.nasa.gov/msl/home

https://www.jpl.nasa.gov/missions/mars-science-laboratory-curiosity-rover-msl

Robert P. Sharp: https://en.wikipedia.org/wiki/Robert_P._Sharp