Tag: Jupiter

Astronomers Have Formula for Finding Subsurface Oceans in Exomoons

Article by Erik Arends                             April 23, 2020                            (phys.org)

• In the search for extraterrestrial life, we have typically looked at Earth-like planets at a distance from their parent star where the temperature is between the freezing and boiling point of water. But as in our own solar system, most of the liquid water seems to be outside of this ‘habitable zone’ on moons where interior water is heated beyond the melting point by tidal forces.

• In our solar system only Mars and Earth have ‘habitable’ surfaces. But moons within our solar system, such as Enceladus, Europa and six other moons of Jupiter, Saturn, Uranus and Neptune, are examples of celestial bodies that are freezing cold on the surface but may harbor habitable subsurface oceans.

• Researchers from SRON Netherlands Institute for Space Research and the University of Groningen (RUG) have derived a formula that indicates whether a subsurface ocean is present on an ‘exomoon’ and how deep it is. Adding moons to the equation, exoplanet hunters have a much larger field of potentially habitable places to search for extraterrestrial life. In fact, “there could be four times as many habitable exomoons as exoplanets,” says lead author Jesper Tjoa.

• The formula analyzes factors including the diameter of the moon, the distance to its planet, the thickness of the gravel layer on the surface, and the thermal conductivity of the ice or soil layer below the surface to provide a lower limit for the ocean depth.

• Just as “astronomers study starlight shining through the atmospheres of exoplanets” to identify oxygen, for example, says Tjoa, future telescopes “may see geysers like on Enceladus, stemming from a subsurface ocean”, as an indication of life there.

 

So far, the search for extraterrestrial life has focused on planets at a distance from their star where liquid water is possible on the surface. But within

              Jesper Tjoa

our Solar System, most of the liquid water seems to be outside this zone. Moons around cold gas giants are heated beyond the melting point by tidal forces. The search area in other planetary systems therefore increases if we also consider moons. Researchers from SRON and RUG have now found a formula to calculate the presence and depth of subsurface oceans in these ‘exomoons.”

In the search for extraterrestrial life, we have so far mainly looked at Earth-like planets at a distance from their parent star where the temperature is between the freezing and boiling point of water. But if we use our own Solar System as an example, moons look more promising than planets. Enceladus, Europa and about six other moons of Jupiter, Saturn, Uranus and Neptune may harbor a subsurface ocean. They all reside far outside the traditional habitable zone—it is literally freezing cold on the surface—but tidal interaction with their host planet heats up their interior.

With moons entering the equation, exoplanet hunters such as the future PLATO telescope—which SRON is also working on—gain hunting ground regarding the search for life. When astronomers find a so-called exomoon, the main question is whether liquid water is possible. Researchers from SRON Netherlands Institute for Space Research and the University of Groningen (RUG) have now derived a formula telling us whether there is a subsurface ocean present and how deep it is.

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There’s Water on Jupiter’s Moon Europa

 

Article by Mihai Andrei                            November 19, 2019                             (zmescience.com)

• NASA has confirmed that Jupiter’s moon Europa contains liquid water, making it one of the most promising places we know for extraterrestrial life. Astronomers have previously observed plumes of water emerging from Europa reaching hundreds of kilometers high.

• More recently, researchers at the W. M. Keck Observatory, atop the dormant Mauna Kea volcano in Hawaii, found a clear signature of water molecules on the moon. Its earthbound spectrograph was able to detect water on Europa by meticulously removing the signatures of water molecules and other “contaminants” within the earth’s atmosphere.

• While “Essential chemical elements…are found all over the solar system,” says NASA scientist Lucas Paganini, liquid water is somewhat hard to find beyond Earth.” Forty years ago, the Voyager snapped a photo of a cracked and shifting geology on Europa, indicating tectonic drifts or even a sub-surface ocean with slabs of ice moving on top of it.

• Avi Mandell, a Goddard planetary scientist on Paganini’s team, said, “[E]ventually, we’ll have to get closer to Europa to see what’s really going on.” In 2025 he and his fellow astronomers will get their wish. NASA’s Clipper mission will launch toward Jupiter to analyze Europa’s habitability, chemistry, and geology. The mission will also help NASA select a landing site for its future Europa lander. The European Space Agency plans to launch its ‘Jupiter Icy Moons Explorer (or “JUICE”) in 2022 to analyze Jupiter’s Galilean moons: Ganymede, Callisto, and Europa. Might these explorers detect life in a moon’s slushy ocean?

 

NASA has confirmed that Jupiter’s moon Europa contains liquid water, making it one of the most promising places we know for extraterrestrial life.

At first glance, not much is happening on Europa. A small, frozen world orbiting Jupiter doesn’t seem like the most interesting place out there. But 40 years ago, the Voyager snapped an intriguing photo of the satellite: its frozen surface wasn’t stale and monotonous, it was cracked and sliced by different features, suggesting active and recent phenomena. Subsequent missions showed even more exciting things.

Despite being undoubtedly bombarded by meteorites, Europa’s surface is largely devoid of craters. This means that something must have erased or eroded them, suggesting some active geology. Not only is Europa active — it has some form of tectonics, and more impressively, it seems to have liquid water. The liquid water isn’t on the surface but rather beneath the frozen surface. The pattern of the cracks observed on Europa’s surface suggest that the frozen surface of the planet is not locked to the rest of the interior, which is exactly what you’d expect to happen if a layer of liquid were to exist beneath the surface.

To make things even more tantalizing, astronomers have observed something which seems to be plumes of water emerging from Europa. Some of the plumes are hundreds of kilometers high, adding even more evidence to the case for water on Europa.

Now, that case is essentially proven. Researchers looking from the W. M. Keck Observatory, atop the dormant Mauna Kea volcano in Hawaii, found a clear signature of water molecules.

“Essential chemical elements (carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur) and sources of energy, two of three requirements for life, are found all over the solar system. But the third — liquid water — is somewhat hard to find beyond Earth,” said Lucas Paganini, a NASA planetary scientist who led the water detection investigation. “While scientists have not yet detected liquid water directly, we’ve found the next best thing: water in vapor form.”

1:46 minute video on ‘Water Plumes on Europa” (NASA Goddard youTube)

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What Is a Dyson Sphere?

Listen to “E65 8-12-19 What Is a Dyson Sphere?” on Spreaker.

Article by Adam Mann                       August 1, 2019                     (space.com)

• In 1960, British-American theoretical physicist Freeman Dyson theorized that as an intelligent alien species’ population increased by 1% per year, their energy needs would grow exponentially becoming a trillion times larger in just 3,000 years. After developing and saturating the local moons and planets in their solar system, they may embark on a longer-term solution: The Dyson sphere.

• A Dyson sphere is a structure with platforms orbiting in tight formation that surrounds and encloses a larger celestial body, such as a gas giant planet like Jupiter or the system’s star itself, like a shell. Such an artificial structure would offer plenty of living space and energy production, drawing from the gas planet or star’s radiation. But as the Dyson sphere absorbed radiation, thereby dimming the planet from an outside observer’s perspective, Dyson theorized that the structure would need to re-radiate this energy through infrared wavelengths to avoid melting the structure itself. Therefore, a Dyson sphere would emit a bright signature in the infrared spectrum while being invisible to the human eye.

• This infrared radiation is considered a type of ‘technosignature’ that astronomers can use to detect an advanced civilization. Since the 1960’s, researchers have scanned infrared maps of the night sky in hopes of spotting a Dyson sphere, without success. But in 2015, Yale University astronomer Tabetha Boyajian did find a distant star that dimmed and flickered. Astronomers speculated that “Tabby’s Star” could be a partially built Dyson sphere. Because other astronomical experiments could not find other technosignatures from the star, scientists now think the object’s light patterns have some kind of non-alien explanation.

• In 1937, Olaf Stapledon first described a “gauze of light traps” surrounding a star system to utilize its solar energy in his novel “Star Maker”. Freeman Dyson acknowledged that this sparked his concept of a Dyson sphere. In 1992, a Dyson sphere was depicted in an episode of “Star Trek: The Next Generation”.

 

A Dyson sphere is a theoretical mega-engineering project that encircles a star with platforms orbiting in tight formation. It is the ultimate solution for living space and energy production, providing its creators ample surface area for habitation and the ability to capture every bit of solar radiation emanating from their central star.

Why build a Dyson sphere?

          Freeman Dyson

Why would anyone construct such a bizarre monstrosity? According to British-American theoretical physicist Freeman Dyson, who first speculated about these putative structures in 1960, an intelligent alien species might consider the undertaking after settling on some moons and planets in their local stellar neighborhood. As their population increased, these extraterrestrials would start to consume ever-greater amounts of energy.

Assuming this alien society’s populace and industry grew at a modest 1% per year, Dyson’s calculations suggested that the aliens’ area and energy needs would grow exponentially, becoming a trillion times larger in just 3,000 years. Should their solar system contain a Jupiter-size body, the species’ engineers could try to figure out how to take the planet apart and spread its mass in a spherical shell.

              Tabetha Boyajian

By building structures at twice the Earth-sun distance, the material would be sufficient to construct a huge number of orbiting platforms 6 to 10 feet (2 to 3 meters) thick, allowing the aliens to live on their star-facing surface. “A shell of this thickness could be made comfortably habitable, and could contain all the machinery required for exploiting the solar radiation falling onto it from the inside,” Dyson wrote.

But after absorbing and exploiting the solar energy, the structure would eventually have to reradiate the energy or else it would build up, causing the sphere to eventually melt, according to Dyson. This means that, to a distant observer, the light of a star wrapped in a Dyson sphere might appear dimmed or even entirely darkened — depending on how dense the orbiting platforms were — while glowing curiously bright in infrared wavelengths that aren’t visible to the naked eye.

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