Jupiter’s moon Europa has an icy shell that conceals a liquid water ocean. Now, scientists have made the first direct measurement of water vapor in Europa’s atmosphere. It’s the best evidence yet for a water plume erupting from the moon’s surface.
The measurements also imply that outside of plume events, Europa’s atmosphere likely has less water vapor overall than previously thought. The scientists describe their findings Monday in Nature Astronomy.
Scientists have known since the 1960s that Europa is home to water ice and, likely, a liquid water ocean beneath the surface. They predicted that radiation from Jupiter would bombard the moon’s icy surface and create water vapor.
And recent studies have turned up indirect evidence that erupting plumes inject water vapor into the moon’s atmosphere. Studies in the past decade have even spotted signs of hydrogen and oxygen in Europa’s atmosphere, but not water vapor directly.
In the new study, researchers used a telescope at the Keck Observatory in Hawaii to search Europa for specific infrared wavelengths of light that water vapor would emit. They observed the moon on 17 different dates from February 2016 to May 2017. Their instruments didn’t pick up signs of water vapor on 16 of those nights. But on April 26, 2016, they measured a large amount — roughly 2,000 metric tons — of water vapor.
Though the researchers didn’t see signs of water vapor on the other 16 nights, that doesn’t mean there wasn’t any. In fact, the researchers believe some water vapor exists in Europa’s atmosphere at all times because of Jupiter’s radiation effect, as previous studies have shown. There was probably just too little water vapor for their instruments to be able to detect.
However, overall, the measurements imply that the typical amount of water vapor in Europa’s atmosphere is probably less than previously thought. This also means that the standout April 2016 measurement likely came from a one-time event, like a water plume.
Upcoming space missions, like Europa Clipper and JUICE (JUpiter ICy moons Explorer), will get a closer look at the moon.
“I’m really looking forward to follow-up studies of Europa and other ocean worlds,” said Lucas Paganini, a NASA planetary scientist and one of the new paper’s authors. “It has been difficult to detect water in liquid form. These detections of water in vapor form, I think, is the closest thing we have in the search for liquid water environments.”
A new study takes a look at the rates of extramarital childbirth in Europe over the past 500 years. This includes children born as the result of adultery — and, spoiler, it’s much lower than you probably think.Read More
In late August, an instrument on the International Space Station, called NICER, spotted its brightest burst of X-ray radiation yet.
NICER, or the Neutron Star Interior Composition Explorer, studies X-rays that come from neutron stars, the super-dense remnants of some stars after they go supernova. This particular burst came from a neutron star called SAX J1808.Read More
It was a typical Japanese summer — hot, humid and cloudy — when archaeologists pulled a well-preserved, fossilized bird from the ground in 2013. Their find, announced this week in Communications Biology, might change our idea of what adaptations were essential to the development of flight.Read More
With the help of sound waves and a small plastic ball, researchers in the U.K. have designed a machine that generates truly 3D holographs.
The whole system is slightly smaller than a shoebox and makes simple images, like a butterfly or smiley face, that are less than an inch tall. Described in Nature, the device is one of the first 3D-image generators that also responds to touch and produces sound, says study coauthor Ryuji Hirayama, a materials science researcher at the University of Sussex.Read More
Ancient Egyptian catacombs stretch for kilometers underground. Branching off of the tunnels are rooms, and those rooms are stacked to the ceilings with jars holding more than 1 million mummified African sacred ibises.
Egyptians buried millions of these leggy, long-beaked birds as prayer offerings to Thoth, the god of wisdom and writing. Early archaeological work and snippets of ancient texts made most historians think these birds were raised in captivity somewhere near the catacombs. But a new analysis, published in the journal PLOSOne, of DNA from the mummified birds shows that the ibises were likely caught in the wild.Read More
NASA announced last week that it will contribute to a European Space Agency mission scheduled to launch in 2028. The spacecraft, called ARIEL (for Atmospheric Remote-sensing Infrared Exoplanet Large-survey), will be the first space mission dedicated to studying exoplanet atmospheres.
During its primary mission lasting some four years, ARIEL will study the atmospheres of roughly 1,000 exoplanets. NASA’s contribution, an instrument called CASE, will let astronomers tell whether these exoplanets’ skies are cloudy, hazy or clear. The results will help astronomers understand how planets and their atmospheres form and change over time.
So far, astronomers have discovered thousands of exoplanets that pass in front of their stars from our point of view. With the right tools, astronomers can study light from the host stars that pass through the planets’ atmospheres. This can reveal information like the chemical makeup and temperatures of these atmospheres as well as what chemical reactions are taking place there.
The James Webb Space Telescope, currently scheduled to launch in 2021, will be able to study exoplanet atmospheres. But since JWST will split its time between multiple projects, it will only focus on studying the atmospheres of a few exoplanets. ARIEL, however, will observe the skies of about 1,000 exoplanets, from rocky planets to Jupiter-like gas giants.
“I’m really looking forward to the ability to place individual planets within a statistical context,” said Mark Swain, an astrophysicist at NASA’s Jet Propulsion Laboratory who is heading production of the CASE instrument. “That is something which you need a large survey of exoplanets to do.”
CASE, which stands for Contribution to ARIEL Survey of Exoplanets, will capture wavelengths of visible and infrared light that carry evidence for clouds and hazes in planets’ skies. What makes something a cloud or haze? Clouds condense out of the atmosphere, like water droplets that make clouds in Earth’s sky. Hazes are molecules that often form through chemical processes when light interacts with molecules in the atmosphere.
Understanding whether an exoplanet has clouds or hazes will help astronomers better interpret other information about the planet’s atmosphere, like chemical makeup and temperature, and figure out what physical and chemical processes are happening.
Also, understanding chemical compositions of exoplanet atmospheres might help decide which of two leading theories for how planets form is most likely correct. One theory suggests that planets will tend to have similar fractions of heavy elements as their host stars, while another implies that the heavy element fractions could be quite different.
Finally, studying the atmospheres of 1,000 planets should help astronomers find out what’s typical and pick out interesting cases to delve into.
“When we see a single planet, a big question is, ‘Is this kind of like the others, or did something special happen here?’” Swain said. “And that’s a fundamental capability that ARIEL is going to give us.”
On November 11, SpaceX launched a Falcon 9 rocket carrying another 60 Starlink satellites, which will eventually provide internet service worldwide. The launch from Cape Canaveral Air Force Station made history by reusing a record number of rocket parts. But even with that feat in aerospace design, the launch wasn’t celebrated by everyone.Read More
If there was a wormhole in the center of our galaxy, how could we tell? Two physicists propose that carefully watching the motions of a star orbiting the Milky Way’s supermassive black hole might help scientists start to check. The researchers published the idea in a recent paper in the journal Physical Review D.
A wormhole is a hypothetical concept that connects two separate areas of space-time. Wormholes often appear in science fiction narratives like the 2014 film Interstellar as a convenient way to get from point A to point B in the vast universe. Physicists have many theories that describe how wormholes might behave, if they exist, but haven’t yet found any.Read More
Thousands of years ago, ancient Egyptians built their agricultural systems around the dependable movement of the Nile. Those rhythms date back much further than any human relative has been alive, scientists now find.
New research shows that the Nile has kept about the same course for its entire 30-million-year existence. This is likely thanks to a reliable flow of rocky material just below the Earth’s surface, which continually pushes up the Ethiopian Highlands, where the river starts, says an international team of researchers.Read More