The Green Skies of Mars and Other Astronomical Wonders

Astronauts on Mars may see a green sky, eerie new study suggests


Using the European Space Agency‘s (ESA) ExoMars Trace Gas Orbiter (TGO), scientists have observed Mars‘ atmosphere glowing green for the first time ever — in the visible light spectrum, that is. The effect is called airglow (or dayglow or nightglow, depending on the hour). Nightglow “occurs when two oxygen atoms combine to form an oxygen molecule,” according to ESA. On Mars, this happens at an altitude of approximately 31 miles (50 km). Scientists have suspected Mars to have airglow for some 40 years, but the first observation only occurred a decade ago by ESA’s Mars Express orbiter, which detected the phenomenon in the infrared spectrum. Then, in 2020, scientists observed the phenomenon in visible light using TGO, but in Martian daylight rather than at night. Now, we’ve seen the phenomenon at night via TGO.

Moon is 40 million years older than we thought, tiny crystals from Apollo mission confirm

The moon is at least 40 million years older than we once thought, a new study reveals. Scientists confirmed our cosmic companion’s new minimum age after reanalyzing tiny impact crystals from lunar samples taken by NASA’s Apollo 17 mission in 1972. Earth is approximately 4.54 billion years old. So based on the newest study, the zircon crystals were formed around 80 million years after our planet formed. However, the collision that birthed the moon could have actually happened even earlier. After the Earth-Thea crash, the infant moon’s surface would have been covered by a magma ocean due to the intense energy of the collision. Therefore, the lunar zircon crystals could only have properly solidified into their current state once the magma ocean had cooled down.

The oldest continents in the Milky Way may be 5 billion years older than Earth’s

Astrobiologists think a planet needs to have certain features to support life: oxygen in its atmosphere, something to shield organisms from dangerous radiation and liquid water, for a start. Although big land masses aren’t strictly necessary for living things to emerge, Earth’s history shows that they’re important for life to thrive and exist for long periods of time. So, if an exoplanet had continents before Earth, it follows that there might be older, more advanced life on that world.

This line of thought led Jane Greaves, an astronomer at Cardiff University astronomer in the U.K., to answer the question: When did the first continents appear on a planet in our galaxy? Turns out, two exoplanets’ continents — and perhaps life — may have arisen four to five billion years before Earth’s.

Can a Dead Star Keep Exploding?
If the Tasmanian Devil is a type of dead star, it’s not behaving like the others. As a dead star, the light coming from it could signal its transition into a sort of stellar afterlife. It could be a new type of stellar corpse.
“Because the corpse is not just sitting there, it’s active and doing things that we can detect,” Ho said. “We think these flares could be coming from one of these newly formed corpses, which gives us a way to study their properties when they’ve just been formed.”
The Echoes From Inflation Could Still Be Shaking the Cosmos Today
In the very early universe, physics was weird. A process known as “inflation,” where best we understand the universe went from a single infinitesimal point to everything we see today, was one such instance of that weird physics. Now, scientists from the Chinese Academy of Science have sifted through 15 years of pulsar timing data in order to put some constraints on what that physics looks like.
Life Might Be Easiest to Find on Planets that Match an Earlier Earth

When methane (CH4) and oxygen (O2) are both present in an atmosphere, it’s an indication that life is at work. That’s because, in an oxygen environment, methane only lasts about 10 years. Its presence indicates disequilibrium. For it to be present, it has to be continually replenished in amounts that only life can produce.

Continue reading “The Green Skies of Mars and Other Astronomical Wonders”

New Evidence on How the Dinosaurs Died

Such a cool article from Universe Today, I think it merits a post all to itself!

Devastating Clouds of Dust Helped End the Reign of the Dinosaurs

When a giant meteor crashed into Earth 66 million years ago, the impact pulverized cubic kilometers of rock and blasted the dust and debris into the Earth’s atmosphere. It was previously believed that sulfur from the impact and soot from the global fires that followed drove a global “impact winter” that killed off 75% of species on Earth, including the dinosaurs.

A new geology paper says that the die-off was additionally fueled by ultrafine dust created by the impact which filled the atmosphere and blocked sunlight for as long as 15 years. Plants were unable to photosynthesize and global temperatures were lowered by 15 degrees C (59 F).

Most scientists agree the disaster started with an asteroid impact, where an asteroid at least 10 kilometers wide struck the Chicxulub region in the present-day Yucatán Peninsula in Mexico. The impact released 2 million times more energy than the most powerful nuclear bomb ever detonated.

The devastation created layer of ash sandwiched between layers of rock, known as the Cretaceous-Paleogene (K–Pg) boundary, formerly known as the Cretaceous–Tertiary (K-T) boundary, which is found across the world in the geologic record. It includes a layer of iridium, an element common in asteroids but rare on Earth. It was this ‘iridium anomaly’ that first revealed the extinction event as an asteroid strike to geologists more than three decades ago.

What has been debated is what created conditions for the post-impact winter. The leading candidates were sulphur from the asteroid’s impact, or soot from global wildfires that ensued after the impact. Both would have blocked out sunlight and plunged the world into a long, dark winter, collapsing the food chain and creating a chain reaction of extinctions.  

Overview of the Cretaceous-Paleogene boundary in North Dakota (USA). The sediments indicate a river and swamp-like environment at the end of the age of the dinosaurs. The pink-brown layer yields ejecta debris derived from the Chicxulub impact event and the grain-size data from this interval were used as input parameters for the paleoclimate modeling study (photo: Pim Kaskes).

But in this new research, scientists from the Royal Observatory of Belgium (ROB) studied new sediment samples taken from the Tanis fossil site in North Dakota in the US, which captures a 20-year period during the aftermath of the asteroid impact. Analysis of the samples revealed evidence of silicate dust particles, particles that were ejected into the atmosphere and eventually settled back down on the planet.

“We specifically sampled the uppermost millimeter-thin interval of the Cretaceous-Paleogene boundary layer,” said Pim Kaskes  from the Archaeology, Environmental Changes & Geo-chemistry (AMGC) at the Vrije Universiteit Brussel (VUB) and the Vrije Universiteit Amsterdam (VUA), who was also involved in the study. “This interval revealed a very fine and uniform grain-size distribution, which we interpret to represent the final atmospheric fall-out of ultrafine dust related to the Chicxulub impact event. The new results show much finer grain-size values than previously used in climate models and this aspect had important consequences for our climate reconstructions.”

Based on their findings, the scientists also created a new paleoclimate computer model that evaluated the roles of sulfur, soot, and silicate dust on the post-impact climate.

Conceptual model of the Chicxulub impact plume showing different stages of (a) production, and (b) transport and deposition of the impact-generated ejecta (not to scale). (c) Paleoclimate model simulations showcasing the time evolution of the dust-induced photosynthetic active radiation flux across the planet following the Chicxulub impact 66 million years ago (modified from Senel et al., 2023; Nature Geoscience).

“The new paleoclimate simulations show that such a plume of micrometric silicate dust could have remained in the atmosphere for up to 15 years after the event, contributing to global cooling of the Earth’s surface by as much as 15 °C in the initial aftermath of the impact,” said Cem Berk Senel from ROB, the lead author of the study.

But while the dust was a contributor to the catastrophic conditions, the sulfur and soot were also a factor.

“We suggest that, together with additional cooling contributions from soot and sulfur, this is consistent with the catastrophic collapse of primary productivity in the aftermath of the Chicxulub impact,” the researchers wrote.

The prolonged disruption in photosynthesis would pose severe challenges for both terrestrial and marine habitats and mass extinctions would occur in groups not adapted to survive the dark, cold, and food-deprived conditions for at least two years. The researchers said this matches the paleontological records, which show that any plants or animals that could enter a dormant phase (for example, through seeds, cysts, or hibernation in burrows) and were able to adapt to an omnivorous diet, or weren’t dependent on one particular food source generally better survived the K-Pg event.

Continue reading “New Evidence on How the Dinosaurs Died”

Planets and Nebulae and Stars, Oh My!

An embarrassment of riches of science articles:

Want to Find Life? Compare a Planet to its Neighbors

With thousands of known exoplanets and tens of thousands likely to be discovered in the coming decades, it could be only a matter of time before we discover a planet with life. The trick is proving it. So far the focus has been on observing the atmospheric composition of exoplanets, looking for molecular biosignatures that would indicate the presence of life. But this can be difficult since many of the molecules produced by life on Earth could also be produced by geologic processes. A new study argues that a better approach would be to compare the atmospheric composition of a potentially habitable world with those of other planets in the star system.

Since planets form within the debris disk of a young star, they will generally have similar compositions. Because of the migration of certain molecules such as water ice, the outer planets can have a slightly different composition than the inner planets, but overall their composition is similar. For this study, the team looked at the abundance of atmospheric carbon among worlds.

Carbon is not just a primary element for life on Earth, it also absorbs readily in water and can be bound geologically in rocks. So the idea is that if an exoplanet is in the potentially habitable zone of a star and has significantly less atmospheric carbon than similar worlds in its system, then that is a strong indicator of the presence of water and organic life. Take our solar system as an example. Earth, Venus, and Mars are all roughly in the habitable zone of the Sun, but both Venus and Mars have atmospheres comprised mostly of carbon dioxide. In contrast, Earth has an atmosphere of mostly nitrogen and oxygen, and only a fraction of a percent of carbon dioxide. Earth’s atmospheric carbon is so dramatically different from that of Venus and Mars that it stands out as a likely inhabited world.

The Crab Reveals Its Secrets To JWSTThe Crab Nebula – otherwise known as the first object on Charles Messier’s list of non-cometary objects or M1 for short

It has been known that there is a pulsar at the core of the nebula, and it’s this pulsar that is the true remains of the progenitor star.  When it went ‘supernova,’ the core collapsed to form the ultra-dense rotating object that, if you happen to be in the right place in space (hey, that rhymes), then you will see a pulse of radiation as it rotates. The infrared images from JWST reveal synchrotron emissions, which are a direct result of the rapidly rotating pulsar.  As the pulsar rotates, the magnetic field accelerates particles in the nebula to astonishingly high speeds such that they emit synchrotron radiation. As a fabulously lucky quirk of nature, the radiation is particularly obvious in infrared, making it ideal for JWST. 


Uranus Has Infrared Auroras, Too

Auroras happen when charged particles in the solar wind and near-planet environment get trapped by a planet’s magnetic field. They funnel down to the atmosphere and collide with gas molecules. This happens on Earth and we see auroras over the north and south poles of our planet. They also happen at other planets. Astronomers detect them on the other giant planets, and a smaller version of them occurs on Mars. Venus probably doesn’t experience similar types of auroral displays, since it has no intrinsic magnetic field. However, it may experience something like them during particularly gusty solar wind events. At the outer planets, the gas mix is different in the atmospheres. That means their aurorae show up in ultraviolet and infrared wavelengths.

Uranus has an interesting magnetic field. It does not originate from the exact center of the planet. It’s also offset by 59 degrees from the rotation axis. That’s tipped 90 degrees from the plane of the solar system. This arrangement means that the Uranian magnetosphere is asymmetric and its field strengths vary depending on location. It connects with the solar wind once every Uranian day (which is 17 hours long). The planet does show some auroral activity, particularly around the poles and Hubble Space Telescope detected some in 2011

Three Planets Around this Sunlike Star are Doomed. Doomed!According to new research we can start writing the eulogy for four exoplanets around a Sun-like star about 57 light years away. But there’s no hurry; we have about one billion years before the star becomes a red giant and starts to destroy them.

The star is Rho Coronae Borealis, a yellow dwarf star like our Sun. It’s in the constellation Corona Borealis, and has almost the same mass, radius, and luminosity as the Sun. The difference is in their ages. The Sun is about five billion years old, but Rho CrB is twice that, which means its red giant phase is imminent, at least in astrophysical terms.

Post main sequence stellar evolution can result in dramatic, and occasionally traumatic, alterations to the planetary system architecture, such as tidal disruption of planets and engulfment by the host star,” Kane writes. Rho Coronae Borealis is both old and bright, making it “… a particularly interesting case of advanced main sequence evolution,” according to Kane. Not only because its similar to the Sun and easily observed, but also because it hosts four exoplanets.


White Dwarfs Could Support Life. So Where are All Their Planets?

Astronomers have found plenty of white dwarf stars surrounded by debris disks. Those disks are the remains of planets destroyed by the star as it evolved. But they’ve found one intact Jupiter-mass planet orbiting a white dwarf.

Are there more white dwarf planets? Can terrestrial, Earth-like planets exist around white dwarfs?

A white dwarf (WD) is the stellar remnant of a once much-larger main sequence star like our Sun. When a star in the same mass range as our Sun leaves the main sequence, it swells up and becomes a red giant. As the red giant ages and runs out of nuclear fuel, it sheds its outer layers as a planetary nebula, a shimmering veil of expanding ionized gas that everybody’s seen in Hubble images. After about 10,000 years, the planetary nebula dissipates, and all that’s left is a white dwarf, alone in the center of all that disappearing glory.

White dwarfs are extremely dense and massive, but only about as large as Earth. They’ve left their life of fusion behind, and emit only residual heat. But still, heat is heat, and white dwarfs can have habitable zones, though they’re very close.

Astronomers are pretty certain that most stars have planets. But those planets are in peril when they orbit a star that leaves the main sequence behind and becomes a red giant. That can wreak havoc on planets, consuming some of them and tearing others apart by tidal disruption. Some white dwarfs are surrounded by debris disks, and they can only be the remains of the star’s planets, ripped to pieces by the star during its red dwarf stage.

But in 2020 researchers announced the discovery of an intact planet among the debris disk in the habitable zone around the white dwarf WD1054-226. If there’s one, there are almost certainly others out there somewhere. Why haven’t we found them? And does the fact that the first one we’ve found is a Jupiter-mass planet mean the WD exoplanet population is dominated by them?

Old Data from Kepler Turns Up A System with Seven PlanetsNASA’s Kepler mission ended in 2018 after more than nine years of fruitful planet-hunting. The space telescope discovered thousands of planets, many of which bear its name. But it also generated an enormous amount of data that exoplanet scientists are still analyzing.

Kepler 385 is similar to the Sun but a little larger and hotter. It’s 10% larger and about 5% hotter. It’s one of a very small number of stars with more than six planets or planet candidates orbiting it.

The two innermost planets are both slightly larger than Earth. According to the new catalogue, they’re both probably rocky. They may even have atmospheres, though if they do, they’re very thin. The remaining five planets have radii about twice as large as Earth’s and likely have thick atmospheres.

Trojan Planets, Diamond Stars, and Other Astronomical Wonders

1st known ‘Trojan’ planets discovered locked in the exact same orbit around a star

Astronomers have discovered the first evidence of ultra-rare ‘Trojan’ planets: two sibling planets bound on the same orbit around the same star.

The potential co-orbiting planets, dancing around the young star PDS 70 roughly 370 light-years away, consist of a Jupiter-size planet and a cloud of debris — possibly the shattered remains of a dead planet, or the gathering building blocks of one yet to be born.

Trojan planets get their unusual name from the two asteroid clusters seen around Jupiter, which, upon their discovery, were split into Greeks and Trojans (the opposing sides of the mythical Trojan War in Homer’s Iliad) based on their proximity to the gas giant’s gravitationally stable Lagrange points.

Lagrange points are places in a solar system where the gravitational pulls of a star and an orbiting planet balance out the motion of an object’s orbit, trapping the object so that it moves in lock-step with the planet.


White dwarfs are truly strange objects. After a lifetime of billions of years of fusion, they transform themselves into something else completely different. They transition from blazing balls of plasma to degenerate lumps of carbon that eventually crystallize into diamonds that last for unimaginably long time periods.

It takes a quadrillion years for a white dwarf to crystallize, and since the Universe is not even 14 billion years old, astronomers will never spot a fully crystallized one. But this research removes some of the mystery by finding one that’s just starting to become a cosmic diamond. Curious astronomers will study more of these bizarre stellar remnants, and one day, we may know exactly how and when something so strange can happen.

A skyscraper-size asteroid flew closer to Earth than the moon — and scientists didn’t notice until 2 days later

Now dubbed 2023 NT1, the roughly 200-foot-wide (60 meters) space rock sailed past our planet on July 13, traveling at an estimated 53,000 mph (86,000 km/h), according to NASA. However, because the rock flew toward Earth from the direction of the sun, our star’s glare blinded telescopes to the asteroid’s approach until long after it had passed.

Astronomers didn’t catch wind of the building-size rock until July 15, when a telescope in South Africa — part of the Asteroid Terrestrial-impact Last Alert System (ATLAS), an array of telescopes designed to spot asteroids several days to weeks before any potential impact — caught the rock making its exit from our neighborhood. More than a dozen other telescopes also spotted the rock shortly afterward, according to the International Astronomical Union’s Minor Planet Center.

Hundreds of ‘ghost stars’ haunt the Milky Way’s center. Scientists may finally know why

“Planetary nebulas offer us a window into the heart of our galaxy and this insight deepens our understanding of the dynamics and evolution of the Milky Way’s bulge region,” University of Manchester astrophysicist Albert Zijlstra said in a statement.

Studying 136 planetary nebulas in the thickest part of the Milky Way, the galactic bulge, with the Very Large Telescope (VLT), the team discovered that each is unrelated and comes from different stars, which died at different times and spent their lives in different locations.

The researchers also found that the shapes of these planetary nebulas line up in the sky in the same way. Not only this, but they are also aligned almost parallel to the plane of the Milky Way.

Love Letters from Space Telescopes

 What an age we live in!

A spectacular trio of merging galaxies in the constellation Boötes takes center stage in this image from the NASA/ESA Hubble Space Telescope. These three galaxies are set on a collision course and will eventually merge into a single larger galaxy, distorting one another’s spiral structure through mutual gravitational interaction in the process. An unrelated foreground galaxy appears to float serenely near this scene, and the smudged shapes of much more distant galaxies are visible in the background. Image Credit: ESA/Hubble & NASA, M. Sun. Article here.

On March 1, 2023, NASA’s Juno spacecraft flew by Jupiter’s moon Io, coming within 51,500 km (32,030 miles) of the innermost and third-largest of the four Galilean moons. The stunning new images provide the best and closest view of the most volcanic moon in our Solar System since the New Horizons mission flew past Io and the Jupiter system in 2006 on its way to Pluto.

Jupiter’s moon Io, as seen by the JunoCam instrument on Juno, on March 1, 2023. Credit: NASA/JPL-Caltech/SwRI/MSSS/ processed by Kevin M. Gill.
Cleary, Io still looks like a pizza. The mottled and colorful surface comes from the volcanic activity, with hundreds of vents and calderas on the surface that create a variety of features. Volcanic plumes and lava flows across the surface show up in all sorts of colors, from red and yellow to orange and black. Some of the lava “rivers” stretch for hundreds of kilometers

Glimpsed only occasionally at the hearts of massive clusters of galaxies, ultramassive black holes are some of the largest and most elusive objects in the universe. These black hole behemoths have masses exceeding that of 10 billion suns, making them far more monstrous than even the supermassive black holes found at the centers of galaxies like the Milky Way, and their tremendous size has long perplexed astronomers.

Now, researchers studying a rare galaxy merger with three supermassive black holes at its center may have finally discovered the origins of these cosmic monsters.

Using a high-resolution cosmological simulation called ASTRID, the team modeled the evolution of the universe as it appeared about 11 billion years ago. In the simulation, the team witnessed the birth of an ultramassive black hole following the merger of the three galaxies. Each of these galaxies contained its own quasar, a supermassive black hole that feeds on gas and powers massive outbursts of radiation that can outshine all the stars in their host galaxies combined.

Let’s Build a World: New Astronomical Finds for Your SF Stories

I’ve got a file (actually a dozen files) of cool science stories that I might use in science fictional world-building. What sf author doesn’t? Even fantasy stories need good science. For instance, an urban fantasy involving werewolves really should depict the phases of the moon accurately. This week, images and data from the Hubble and James Webb Space Telescopes have furnished a treasure trove of research ideas. Rather than post them separately, I’ve gathered a few that I find particularly exciting.


There Could be Many Water Worlds in the Milky Way

Astronomers are curious about how many terrestrial planets in our galaxy are actually “water worlds.”
These are rocky planets that are larger than Earth but have a lower density, which suggests that volatiles like water make up a significant amount (up to half) of their mass-fraction. According to a recent study by researchers from the University of Chicago and the Instituto de Astrofísica de Canarias (IAC), water worlds may be just as common as “Earth-like” rocky planets. These findings bolster the case for exoplanets that are similar to icy moons in the Solar System (like Europa) and could have significant implications for future exoplanet studies and the search for life in our Universe.

“We have discovered the first experimental proof that there is a population of water worlds, and that they are in fact almost as abundant as Earth-like planets. We found that it is the density of a planet and not its radius, as was previously thought, which separates dry planets from wet ones. The Earth is a dry planet, even though its surface is mostly covered in water, which gives it a very wet appearance. The water on Earth is only 0.02% of its total mass, while in these water worlds it is 50% of the mass of the planet.”

However, planets around M-type stars typically orbit so closely that they are tidally locked, where one side is constantly facing toward its sun. At this distance, any water on the planet’s surface would likely exist in a supercritical gas phase, increasing their sizes. As a result, Luque and Pallé theorized that in this population, water is bound to the rock or in closed volumes below the surface, not in the form of oceans, lakes, and rivers on the surface. These conditions are similar to what scientists have observed with icy moons in the outer Solar System, such as Jupiter’s moon Europa and Saturn’s moon Titan.

Given that they are tidally locked to their suns, these planets may also have liquid oceans on their sun-facing side but frozen surfaces everywhere else – colloquially known as “eyeball planets.” While astronomers have speculated about the existence of this class of exoplanet, these findings constitute the first confirmation for this new type of exoplanet. They also bolster the growing case for water worlds that form beyond the so-called “snow line” in star systems (the boundary beyond which volatile elements freeze solid), then migrate closer to their star.

In the past, glaciers may have existed on the surface of Mars, providing meltwater during the summer to create the features we see today. Credit: NASA/JPL-Caltech/ESA

Mars Had Moving Glaciers, but They Behaved Differently in the Planet’s Lower Gravity

On Earth, shifts in our climate have caused glaciers to advance and recede throughout our geological history (known as glacial and inter-glacial periods). The movement of these glaciers has carved features on the surface, including U-shaped valleys, hanging valleys, and fjords. These features are missing on Mars, leading scientists to conclude that any glaciers on its surface in the distant past were stationary. However, new research by a team of U.S. and French planetary scientists suggests that Martian glaciers did move more slowly than those on Earth.

These findings demonstrate how glacial ice on Mars would drain meltwater much more efficiently than glaciers on Earth. This would largely prevent lubrication at the base of the ice sheets, which would lead to faster sliding rates and enhanced glacial-driven erosion. In short, their study demonstrated that lineated landforms on Earth associated with glacial activity would not have had time to develop on Mars.
In addition to explaining why Mars lacks certain glacial features, the work also has implications for the possibility of life on Mars and whether that life could survive the transition to a global cryosphere we see today. According to the authors, an ice sheet could provide a steady water supply, protection, and stability to any subglacial bodies of water where life could have emerged. They would also protect against solar and cosmic radiation (in the absence of a magnetic field) and insulation against extreme variations in temperature.

Continue reading “Let’s Build a World: New Astronomical Finds for Your SF Stories”

What’s New With Voyager 1?

 Voyager 1 is no Longer Sending Home Garbled Data!

This aging and still-valuable spacecraft has been exploring the outer parts of the solar system since its launch in 1977, along with its twin sibling, Voyager 2. They each traveled slightly different trajectories. Both went past Jupiter and Saturn, but Voyager 2 continued on to Uranus and Neptune. They’re both now outside the solar system, sending back data about the regions of space they’re exploring.

Voyager 1 flew past Jupiter in March 1979, and Saturn in November 1980. After its close approaches to those two gas giants, it started a trajectory out of the solar system and entered interstellar space in 2013. That’s when it ceased to detect the solar wind and scientists began to see an increase in particles consistent with those in interstellar space.

These days, Voyager 1 is more than 157.3 astronomical units from Earth and moving out at well over 61,000 km/hour. It’s busy collecting data about the interstellar medium and radiation from distant objects. If all goes well, the spacecraft should continue sending back data for nearly a decade. After that, it should fall silent as it travels beyond the Oort Cloud and out to the stars.

Earlier this year, however, the teams attached to the Voyager 1 mission noticed that the spacecraft was sending weird readouts about its attitude articulation and control system (called AACS, for short). Essentially, the AACS was sending telemetry data all right, but it was routing it to the wrong computer, one that had failed years ago. This corrupted the data, which led to the strangely garbled messages the ground-based crew received.

Once the engineers figured out that the old, dead computer might have been part of the problem, they had a way forward. They simply told the AACS to switch over sending to the correct computer system. The good news was that it didn’t affect science data-gathering and transmission. The best news came this week: team engineers have fixed the issue with the AACS and the data are flowing normally again.

The ongoing issue with AACS didn’t set off any fault protection systems onboard the spacecraft. If it had, Voyager 1 would have gone into “safe mode” while engineers tried to figure out what happened. During the period of garbled signals, AACS continued working, which indicated that the problem was either upstream or downstream of the unit. The fact that data were garbled provided a good clue to related computer issues.

This adapted article appeared in Universe Today. Click through for the full thing.