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Frontier Adventure

Juno Reveals Secrets About Europa’s Icy Surface

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Europa has always held a fascination to me. I think it’s the concept of a world with a sub-surface ocean and the possibility of life that has inspired me and many others. In September 2022, NASAs Juno spacecraft made a flyby, coming within 355 kilometres of the surface. Since the encounter, scientists have been exploring the images and have identified regions where brine may have bubbled to the surface. Other images revealed possible, previously unidentified steep-walled depressions up to 50km wide, this could be caused by a free-floating ocean! 

Juno was launched to Jupiter on 5 August 2011. It took off from the Cape Canaveral site on board an Atlas V rocket and travelled around 3 billion kilometres. It arrived at Jupiter on 4 July 2016 and in September 2022 made its closest flyby of Europa. The frozen world is the second of the four Galilean satellites that were discovered by Galileo over 400 years ago. Visible in small telescopes, the true nature of the moon is only detectable by visiting craft like Juno. 

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Artist’s impression of NASA’s Galileo space probe in orbit of Jupiter. Credit: NASA

During its close fly-by, one of the onboard cameras known as Juno-Cam took the highest resolution images of the moon since Galileo took a flyby in 2000. The images supported the long held theory that the icy crusts at the north and south poles are not where they used to be. Another instrument on board, known as the Stellar Reference Unit (SRU), revealed possible activity resembling plumes where brine may have bubbled to the surface.

The ground track over Europa that was followed by Juno enabled imaging around the equatorial regions. The images revealed the usual, expected blocks of ice, walls, ridges and scarps but also found something else. Steep walled depressions that measured 20 to 50 kilometres across were also seen and they resembled large ovoid pits. 

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One of Juno’s enormous solar panels, unfurled on Earth. NASA/JPL. SWrI

The observations of the meanderings of the north/south polar ice and the varied surface features all point towards an outer icy shell that is free-floating upon the sub surface ocean. This can only happen if the outer shell is not connected to the rocky interior. When this happens, there are high levels of stress on the ice which then causes the fracture pattern witnessed. The images represent the first time such patterns have been seen in the southern hemisphere, the first evidence of true polar wandering.

The images from the SRU surprisingly provided the best quality images. It was originally designed to detect faint light from stars for navigation. Instead, the team used it to capture images when Europa was illuminated by the gentle glow of sunlight reflected from Jupiter. It was quite a novel approach and allowed complex features to become far more pronounced than before. Intricate networks of ridges criss-crossing the surface were identified along with dark stains from water plumes. One feature in particular stood out, nicknamed ‘the Platypus’, it was a 37 kilometre by 67 kilometre region shaped somewhat like a platypus.

Source : NASA’s Juno Provides High-Definition Views of Europa’s Icy Shell

The post Juno Reveals Secrets About Europa’s Icy Surface appeared first on Universe Today.

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Webb Sees Black Holes Merging Near the Beginning of Time


A long time ago, in two galaxies far, far away, two massive black holes merged. This happened when the Universe was only 740 million years old. A team of astronomers used JWST to study this event, the most distant (and earliest) detection of a black hole merger ever.

Such collisions are fairly commonplace in more modern epochs of cosmic history and astronomers know that they lead to ever-more massive black holes in the centers of galaxies. The resulting supermassive black holes can contain millions of billions of solar masses. They affect the evolution of their galaxies in many ways.

Using JWST and HST, astronomers have found behemoth black holes earlier and earlier in cosmic time, within the first billion years of the Universe’s history. That raises the question: how did they get so massive so fast? Black holes accrete matter as they grow, and for the most supermassive ones, their colliding galaxies are part of that matter-harvesting history.

What JWST Shows Us about Early Black Holes Merging

The most recent JWST observations focused on a system called ZS7. It’s a galaxy merger where two very early systems come together, complete with colliding black holes. This is not something astronomers can detect with ground-based telescopes. The merger itself lies quite far away. Plus, the expansion of the Universe stretches its light into the infrared part of the electromagnetic spectrum. That makes it inaccessible from Earth’s surface. However, infrared is detectable with JWST’s Near-infrared Spectrometer (NIRSpec). It can find signatures of mergers in the early Universe, according to astronomer Hannah Übler of the University of Cambridge in the United Kingdom.

Zeroing in on the ZS7 galaxy system and the colliding black holes. Courtesy: The field in which the ZS7 galaxy merger was observed by JWST. Courtesy ESA/Webb, NASA, CSA, J. Dunlop, D. Magee, P. G. Pérez-González, H. Übler, R. Maiolino, et. al
Zeroing in on the ZS7 galaxy system and the colliding black holes. Courtesy: The field in which the ZS7 galaxy merger was observed by JWST. Courtesy ESA/Webb, NASA, CSA, J. Dunlop, D. Magee, P. G. Pérez-González, H. Übler, R. Maiolino, et. al

“We found evidence for very dense gas with fast motions in the vicinity of the black hole, as well as hot and highly ionized gas illuminated by the energetic radiation typically produced by black holes in their accretion episodes,” said Übler, who is lead author on a paper about the discovery. “Thanks to the unprecedented sharpness of its imaging capabilities, Webb also allowed our team to spatially separate the two black holes.”

Those black holes are pretty massive: one contains about 50 million solar masses. The other probably has about the same mass, but it’s hard to tell because it’s embedded in a dense gas region. The stellar masses of the galaxies puts them in about the same stellar-mass population as the nearby Large Magellanic Cloud, according to astronomer Pablo G. Pérez-González of the Centro de Astrobiología (CAB), CSIC/INTA, in Spain. “We can try to imagine how the evolution of merging galaxies could be affected if each galaxy had one supermassive black hole as large or larger than the one we have in the Milky Way”.

Other Implications of Black Hole Mergers at Cosmic Dawn

The analysis of the JWST observations reinforces the idea that mergers are an important way for black holes to grow. That’s particularly true in the early Universe, according to Ühler. “Together with other Webb findings of active, massive black holes in the distant Universe, our results also show that massive black holes have been shaping the evolution of galaxies from the very beginning.”

Many active galactic nuclei (AGN) in the very early Universe are associated with somewhat massive black holes. These are likely part of a general merger process in early epochs. Astronomers want to know when these mergers began. That would help them pinpoint the growth of the central supermassive black holes. Mergers of that kind are a likely route for the growth of black holes so early in cosmic time.

An artist's impression of two merging black holes. Image: NASA/CXC/A. Hobart
An artist’s impression of two merging black holes. Image: NASA/CXC/A. Hobart

That’s why astronomers are so anxious to spot them with JWST and future telescopes. They hold the key to understanding the evolution of galaxies and black holes in the infancy of the Universe. Uhler and her team members point this out in their paper, saying: “Our results seem to support a scenario of an imminent massive black
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Linking Organic Molecules to Hydrothermal Vents on Enceladus

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Despite the vast distance between us and Saturn’s gleaming moon Enceladus, the icy ocean moon is a prime target in our search for life. It vents water vapour and large organic molecules into space through fissures in its icy shell, which is relatively thin compared to other icy ocean moons like Jupiter’s Europa. Though still out of reach, scientific access to its ocean is not as challenging as on Europa, which has a much thicker ice shell.

The presence of large organic molecules isn’t very controversial. But they don’t necessarily signify that something alive lurks in its ancient, unseen ocean. Instead, hydrothermal processes could produce them. The complexity arises because hydrothermal processes are also linked to the emergence of life.

Understanding the abiotic processes that produce these molecules is important not just for Enceladus. It could serve as a baseline for understanding the results of a future mission to the frozen moon and any biosignatures it might detect.

New research in the journal Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences examines this issue. It’s titled “Laboratory characterization of hydrothermally processed oligopeptides in ice grains emitted by Enceladus and Europa.” The lead author is Dr. Nozair Khawaja from the Institute of Space Systems (IRS) at the University of Stuttgart.

Scientists postulate the life on Earth got started at hydrothermal events on the ocean floor. These vents provide mineral-rich fluids. At deep ocean vents under extreme pressure, these minerals can react with seawater to produce the building blocks of life.

This image shows a black smoker hydrothermal vent discovered in the Atlantic Ocean in 1979. It's fueled from deep beneath the surface by magma that superheats the water. The plume delivers minerals to the sea. Courtesy USGS.
This image shows a black smoker hydrothermal vent discovered in the Atlantic Ocean in 1979. It’s fueled from deep beneath the surface by magma that superheats the water, and the plume delivers minerals to the sea. Courtesy USGS.

“In research, we also speak of a hydrothermal field,” explains lead author Khawaja. “There is convincing evidence that conditions prevail in such fields that are important for the emergence or maintenance of simple life forms.”

Much of what we know about Enceladus comes from the Cassini mission. Scientists are still working with Cassini’s data even though it ended in 2017. Although much of the data was low resolution, it’s still valuable.

Professor Frank Postberg from the Freie Universität (FU) Berlin is one of the study’s co-authors. “In 2018 and 2019, we encountered various organic molecules, including some that are typically building blocks of biological compounds,” Postberg said. “And that means it is possible that chemical reactions are taking place there that could eventually lead to life.”

There’s a missing link between the hydrothermal vents and the molecules vented into space. Scientists aren’t certain if the vents are responsible for the molecules or in what way. Is life involved?

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This image shows the detection of hydrothermally altered biosignatures on Enceladus. Image Credit: SWRI/NASA/JPL

To answer these questions, the researchers simulated an Enceladus hydrothermal vent in their laboratory.

“To this end, we simulated the
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