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On July 1st, 2023, the European Space Agency (ESA) launched the Euclid Observatory, a mission that will spend the next six years investigating the composition and evolution of the Universe. In particular, Euclid will observe how the Universe has expanded over the past 10 billion years to test theories about Dark Energy. While fine-tuning and calibrating the telescope’s instruments in preparation for the mission’s first survey, the mission team noticed that a few layers of water ice formed on its mirrors after it entered the freezing cold of space.

While common, this is a problem for a highly sensitive mission like Euclid, which requires remarkable precision to investigate cosmic expansion. After months of research, the Euclid team tested a newly designed procedure to de-ice the mission’s optics. On March 20th, the ESA announced that the team’s de-icing approach worked (so far) and that Euclid’s vision has been restored. If the method proves successful, it will have validated the mission team’s plan to keep Euclid‘s optical system working for the rest of its mission.

The problem first became evident as science operations experts noticed a small but progressive decrease in light measured by the telescope’s VISible instrument (VIS). This instrument is responsible for measuring visible light from distant galaxies to determine how the light’s trajectory is affected by gravity fields. Mischa Schirmer, a calibration scientist for the Euclid consortium and one of the main designers of the new de-icing plan, explained in an ESA press release:

“We compared the starlight coming in through the VIS instrument with the recorded brightness of the same stars at earlier times, seen by both Euclid and ESA’s Gaia mission. Some stars in the Universe vary in their luminosity, but the majority are stable for many millions of years. So, when our instruments detected a faint, gradual decline in photons coming in, we knew it wasn’t them – it was us.”

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Artist’s impression of the Euclid observatory. Credit: ESA

It was always expected that there would be some water contamination with Euclid, which is why there was an “outgassing campaign” shortly after launch. This consisted of the telescope being warmed up by onboard heaters and also partially exposed to the Sun, sublimating most of the water brought from Earth. However, a considerable amount remained after being absorbed in the telescope’s multi-layer insulation, which slowly began building up on the VIS intrument’s mirror surfaces. After months of research, lab studies, and calibrations, the team determined the source and began working on a solution.

The obvious solution was to heat Euclid again by running all its internal heaters for days. However, this ran the risk of deforming the mechanical structure of the spacecraft, which could alter Euclid’s optical alignment. Said Andreas Rudolph, Euclid Flight Director at ESA’s mission control:

“Most other space missions don’t have such demanding requirements on ‘thermo-optical stability’ as Euclid. To fulfil Euclid’s scientific goals of making a 3D map of the Universe by observing billions of galaxies out to 10 billion light-years, across more than a third of the sky, means we have to keep the mission incredibly stable – and that includes its temperature. Switching on the heaters in the payload module therefore needs to be done with extreme care.”

The team began by individually heating two of Euclid’s mirrors independently, a low-risk approach since they are located in areas where water vapor was not likely to contaminate other instruments. After analyzing the initial results, the team found that Euclid’s vision was restored to its previous accuracy. However, this was a temporary solution, and a long-term strategy for regular de-icing is still being sought. In the meantime, the ESA promises to continue to monitor the telescope for changes and share any new findings publicly.

However, the response to this problem highlights the international cooperation that made this mission possible. Said Ralf Kohley, Euclid Instrument Operations Scientist who coordinated the
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Juno Reveals a Giant Lava Lake on Io

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NASA’s Juno spacecraft came within 1,500 km (930 miles) of the surface of Jupiter’s moon Io in two recent flybys. That’s close enough to reveal new details on the surface of this moon, the most volcanic object in the Solar System. Not only did Juno capture volcanic activity, but scientists were also able to create a visual animation from the data that shows what Io’s 200-km-long lava lake Loki Patera would look like if you could get even closer. There are islands at the center of a magma lake rimmed with hot lava. The lake’s surface is smooth as glass, like obsidian.

“Io is simply littered with volcanoes, and we caught a few of them in action,” said Juno principal investigator Scott Bolton during a news conference at the European Geophysical Union General Assembly in Vienna, Austria. “There is amazing detail showing these crazy islands embedded in the middle of a potentially magma lake rimmed with hot lava. The specular reflection our instruments recorded of the lake suggests parts of Io’s surface are as smooth as glass, reminiscent of volcanically created obsidian glass on Earth.”

This animation is an artist’s concept of Loki Patera, a lava lake on Jupiter’s moon Io, made using data from the JunoCam imager aboard NASA’s Juno spacecraft. With multiple islands in its interior, Loki is a depression filled with magma and rimmed with molten lava. Credit: NASA/JPL-Caltech/SwRI/MSSS

Just imagine if you could stand by the shores of this lake – which would be a stunning view in itself. But then, you could look up and see the giant Jupiter looming in the skies above you.

Juno made the two close flybys of Io in December 2023 and February 2024. Images from Juno’s JunoCam included the first close-up images of the moon’s northern latitudes. Undoubtedly, Io looks like a pizza – which has been the conclusion since our first views of this moon, when Voyager 1 flew through the Jupiter system in March 1979. 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.

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Io’s sub-Jovian hemisphere is revealed in detail for the first time since Voyager 1 flew through the Jupiter system in March 1979, during the Juno spacecraft’s 58th perijove, or close pass, on February 3, 2024. This image shows Io’s nightside illuminated by sunlight reflected off Jupiter’s cloud tops. Several surface changes are visible include a reshaping of the compound flow field at Kanehekili (center left) and a new lava flow to the east of Kanehekili. This image has a pixel scale of 1.6 km/pixel. Credit : NASA/SwRI/JPL/MSSS/Jason Perry.

Juno scientists were also able to re-create a spectacular feature on Io, a spired mountain that has been nicknamed “The Steeple.” This feature is between 5 and 7 kilometers (3-4.3 miles) in height. It’s hard to comprehend the type of volcanic activity that could have created such a stunning landform.

Created using data collected by the JunoCam imager aboard NASA’s Juno during flybys in December 2023 and February 2024, this animation is an artist’s concept of a feature on the Jovian moon Io that the mission science team nicknamed “Steeple Mountain.” Credit: NASA/JPL-Caltech/SwRI/MSSS

Speaking of volcanic activity, two recent papers have come to a jaw-dropping conclusion about Io: this moon has been erupting since the dawn of the Solar System.

All the volcanic on Io is activity is driven by tidal heating. Io is in an orbital resonance with two other large moons of Jupiter, Europa and Ganymede.

“Every time Ganymede orbits Jupiter once, Europa orbits twice, and Io orbits four times,” explained the authors of a paper published in the Journal of Geophysical Research: Planets, led by Ery Hughes of GNS Science in New Zealand. “This situation causes tidal heating in Io (like how the Moon causes ocean tides on Earth), which causes the volcanism.”

However, scientists haven’t known how long this resonance has been occurring and whether what we observe today is what has always been happening in the Jupiter system. This is because volcanism renews Io’s surface almost

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Artemis Astronauts Will Deploy New Seismometers on the Moon

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Back in the 1960s and 1970s, Apollo astronauts set up a collection of lunar seismometers to detect possible Moon quakes. These instruments monitored lunar activity for eight years and gave planetary scientists an indirect glimpse into the Moon’s interior. Now, researchers are developing new methods for lunar quake detection techniques and technologies. If all goes well, the Artemis astronauts will deploy them when they return to the Moon.

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Fiber optic cable is the heart of a seismology network to be deployed on the Moon by future Artemis astronauts.

The new approach, called distributed acoustic sensing (DAS), is the brainchild of CalTech geophysics professor Zhongwen Zhan. It sends laser beams through a fiber optic cable buried just below the surface. Instruments at either end measure how the laser light changes during the shake-induced tremors. Basically Zhan’s plan turns the cable into a sequence of hundreds of individual seismometers. That gives precise information about the strength and timing of the tremors. Amazingly, a 100-kilometer fiber optic cable would function as the equivalent of 10,000 seismometers. This cuts down on the number of individual seismic instruments astronauts would have to deploy. It probably also affords some cost savings as well.

A seismometer station deployed on the Moon during the Apollo 15 mission. Courtesy NASA.
A seismometer station deployed on the Moon during the Apollo 15 mission. Courtesy NASA.

DAS and Apollo on the Moon

Compare DAS the Apollo mission seismometer data and it becomes obvious very quickly that DAS is a vast improvement. In the Apollo days, the small collection of instruments left behind on the Moon provided information that was “noisy”. Essentially, when the seismic waves traveled through different parts of the lunar structure, they got scattered. This was particularly true when they encountered the dusty surface layer. The “noise” basically muddied up the signals.

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The layout for the Apollo Lunar Seismic Profiling Experiment for the Apollo 17 mission. Courtesy Nunn, et al.

What DAS Does to Detect Quakes on the Moon

The DAS system stations laser emitters and data collectors at each end of a fiber optic cable. This allows for multiple widely spaced installations that measure light as it transits the network. The cable consists of glass strands, and each strand contains tiny imperfections. That sounds bad, but each imperfection provides a useful “waypoint” that reflects a little bit of the light back to the source. That information gets recorded as part of a larger data set. Setting up such a system of
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Ice Deposits on Ceres Might Only Be a Few Thousand Years Old

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The dwarf planet Ceres has some permanently dark craters that hold ice. Astronomers thought the ice was ancient when they were discovered, like in the moon’s permanently shadowed regions. But something was puzzling.

Why did some of these shadowed craters hold ice while others did not?

Ceres was first discovered in 1801 and was considered a planet. Later, it was thought to be the first asteroid ever discovered, since it’s in the main asteroid belt. Since then, our expanding knowledge has changed its definition: we now know it as a dwarf planet.

Even though it was discovered over 200 years ago, it’s only in the last couple of decades that we’ve gotten good looks at its surface features. NASA’s Dawn mission is responsible for most of our knowledge of Ceres’ surface, and it found what appeared to be ice in permanently shadowed regions (PSRs.)

New research shows that these PSRs are not actually permanent and that the ice they hold is not ancient. Instead, it’s only a few thousand years old.

The new research is titled “History of Ceres’s Cold Traps Based on Refined Shape Models,” published in The Planetary Science Journal. The lead author is Norbert Schorghofer, a senior scientist at the Planetary Science Institute.

“The results suggest all of these ice deposits must have accumulated within the last 6,000 years or less.”

Norbert Schorghofer, senior scientist, Planetary Science Institute.

Dawn captured its first images of Ceres while approaching the dwarf planet in January 2015. At that time, it was close enough to capture images as good as Hubble’s. Those images showed craters and a high-albedo site on the surface. Once captured by Ceres, Dawn followed a polar orbit with decreasing altitude. It eventually reached 375 km (233 mi) above the surface, allowing it to see the poles and surface in greater detail.

“For Ceres, the story started in 2016, when the Dawn spacecraft, which orbited around Ceres at the time, glimpsed into these permanently dark craters and saw bright ice deposits in some of them,” Schorghofer said. “The discovery back in 2016 posed a riddle: Many craters in the polar regions of Ceres remain shadowed all year – which on Ceres lasts 4.6 Earth years – and therefore remain frigidly cold, but only a few of them harbor ice deposits.”

As scientists continued to study Ceres, they made another discovery: its massive Solar System neighbours make it wobble.

“Soon, another discovery provided a clue why: The rotation axis of Ceres oscillates back and forth every 24,000 years due to tides from the Sun and Jupiter. When the axis tilt is high and the seasons strong, only a few craters remain shadowed all year, and these are the craters that contain bright ice deposits,” said lead author Schorghofer.

This figure from the research shows how Ceres' obliquity has changed over the last 25,000 years. As the obliquity varies, sunlight reaches some crater floors that were thought to be PSRs. Image Credit: Schorghofer et al. 2023.
This figure from the research shows how Ceres’ obliquity has changed over the last 25,000 years. As the obliquity varies, sunlight reaches some crater floors that were thought to be PSRs. Image Credit: Schorghofer et al. 2023.

Researchers constructed digital elevation maps (DEMs) of the craters to uncover these facts. They wanted to find out how large and deep the shadows in the craters were, not just now but thousands of years ago. But that’s difficult to do since portions of these craters were in deep shadow when Dawn visited. That made it difficult to see how deep the craters were.

Robert Gaskell, also from the Planetary Science Institute, took on the task. He developed a new technique to create more accurate maps of the craters with data from Dawn’s sensitive Framing Cameras, contributed to the mission by Germany. With improved accuracy, these maps of the crater floors could be used in ray tracing to show sunlight penetrated the shadows as Ceres wobbled over thousands of years.

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