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Is K2-18b Covered in Oceans of Water or Oceans of Lava?

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In the search for potentially life-supporting exoplanets, liquid water is the key indicator. Life on Earth requires liquid water, and scientists strongly believe the same is true elsewhere. But from a great distance, it’s difficult to tell what worlds have oceans of water. Some of them can have lava oceans instead, and getting the two confused is a barrier to understanding exoplanets, water, and habitability more clearly.

 

This brings us to K2-18b, a mini-Neptune orbiting a red dwarf (M dwarf) star about 134 light-years away. The Kepler Space Telescope found it in 2015. NASA’s Exoplanet Catalog describes it as a potentially rocky world almost nine times more massive than Earth. It takes about 30 days to complete one orbit and is about 0.1429 AU from its star.

When it was confirmed as a planet, the authors of the paper presenting the results wrote that “The planet orbiting K2-18 may be an interesting target for atmospheric studies of transiting exoplanets.”

Prophetic words, and when the JWST examined K2-18b’s atmosphere in 2023, it found the carbon-bearing molecules methane and carbon dioxide. “Webb’s discovery adds to recent studies suggesting that K2-18 b could be a Hycean exoplanet, one which has the potential to possess a hydrogen-rich atmosphere and a water ocean-covered surface,” a NASA press release said.

Planetary scientists are very interested in Hycean exoplanets. As things stand now, they’re purely hypothetical. But if scientists could confirm the existence of one of these ocean-bearing planets, the outlook for life elsewhere in our galaxy would change considerably. (If they’re not subject to the runaway greenhouse effect.) If we could reliably find a population of Hycean worlds spread out among the stars, surely that would constitute a powerful signal that life is not confined to Earth.

But there’s a lot of uncertainty regarding Hycean worlds. Do they exist? Can they hold onto their oceans, or are they too hot? Could something else explain the JWST’s atmospheric findings? Why is there a discrepancy between observation and climate modelling? The authors of a new paper point out that, observationally, K2-18b is the archetypal Hycean world. As such, it’s a good place to try to answer some of our scientific questions. The authors say that K2-13b could indeed be an ocean planet, but an ocean of lava rather than water.

The new paper is “Distinguishing oceans of water from magma on mini-Neptune K2-18b.” The lead author is Oliver Shorttle, who studies planetary chemistry at the Institute of Astronomy at Cambridge University. The paper is in pre-print and hasn’t been peer-reviewed yet.

“We propose a solution to this discrepancy between observation and climate modelling by investigating the effect of a magma ocean on the atmospheric chemistry of mini-Neptunes,” the authors write.

K2-18b is a puzzle. Its density is in between Neptune’s and Earth’s, meaning its composition is uncertain. Its density covers a range of possible compositions. JWST observations show that it has a carbon-rich atmosphere and an ammonia-poor atmosphere. These observations are both indicators of an ocean world with a thick H/He atmosphere.

Spectra of K2-18 b, obtained with Webb’s NIRISS (Near-Infrared Imager and Slitless Spectrograph) and NIRSpec (Near-Infrared Spectrograph), display an abundance of methane and carbon dioxide in the exoplanet’s atmosphere. The detection of methane and carbon dioxide and the shortage of ammonia support the hypothesis that there may be a water ocean underneath a hydrogen-rich atmosphere in K2-18 b. Image Credit: NASA, CSA, ESA, R. Crawford (STScI), J. Olmsted (STScI), Science: N. Madhusudhan (Cambridge University)

But there’s another possible explanation: a magma ocean. “We demonstrate that atmospheric NH3 depletion is a natural consequence of the high solubility of nitrogen species in magma at reducing conditions, precisely the conditions prevailing where a thick hydrogen envelope is in communication with a molten planetary surface,” the authors write.

As is so often the case when it comes to atmospheres, the availability of oxygen plays an enormous role. Oxygen is a swinger; it likes to bond with almost anything. Its presence dictates a lot of what happens in an atmosphere.

“How oxidizing a magma is has a profound effect on the solubility of nitrogen,” the authors. Nitrogen is necessary for ammonia to form since ammonia is NH3. So when the JWST found no ammonia in K2-18b’s atmosphere, it may not indicate a Hycean world after all. Instead, it may indicate a magma ocean.

The researchers used models and simulations to try to determine what the JWST observations mean for K2-18b.

This figure from the study shows the relationship between oxygen fugacity and how much nitrogen can stay in the atmosphere of a magma ocean planet. "As oxygen fugacity is decreased, nitrogen's increased solubility depletes the atmosphere by orders of magnitude," the authors explain. (Each coloured circle represents a model run for a given set of parameters.) Image Credit: Shorttle et al. 2024.
This figure from the study shows the relationship between oxygen fugacity and how much nitrogen can stay in the atmosphere of a magma ocean planet. “As oxygen fugacity is decreased, nitrogen’s increased solubility depletes the atmosphere by orders of magnitude,” the authors explain. (Each coloured circle represents a model run for a given set of parameters.) Image Credit: Shorttle et al. 2024.

The researchers found that some of their modelled results of a magma ocean world agree with what the JWST found. “A set of the resulting atmospheres in the magma ocean scenario are consistent with the full transmission spectrum of K2-18b observed by JWST,” they write, adding that “this self-consistent magma ocean model can produce a qualitatively similar transmission spectrum to that observed for K2-18b, and those hypothesized for Hycean planets generally.”

If Shorttle and his colleagues are correct, then a dearth of ammonia can no longer be used to indicate the presence of an ocean on a Hycean world. Ammonia’s profile in an atmosphere can be attributed to both the magma ocean scenario and the water-world scenario. They’re not exclusive.

Artist's depiction of a waterworld. So far, they're only hypothetical and can be confused with magma ocean worlds. We need a way to tell them apart. Credit: David A. Aguilar (CfA)
Artist’s depiction of a waterworld. So far, they’re only hypothetical and can be confused with magma ocean worlds. We need a way to tell them apart. Credit: David A. Aguilar (CfA)

What’s the solution?

“Thus, alternative mutually exclusive chemical tracers of the presence of a water ocean versus a magma ocean should be sought so that future observations can distinguish these potential scenarios,” the researchers write.

The authors think they may have found a chemical tracer that can do the job. They say that finding both CO2 and CO in an exoplanet atmosphere could contra-indicate a magma ocean. “One such possible tracer, and source of potential misfit of the magma ocean scenario with the observed spectrum of K2-18b, is the co-existence of CO2 and CO,” they explain. The problem is that the presence of any CO in K2-18b’s atmosphere is uncertain.

The researchers have shown that we can’t rely on the detection of carbon and the non-detection of ammonia to indicate a Hycean world because, in some circumstances, a magma ocean can produce the same atmospheric chemical profile. What can be done?

Better data and more research, of course.

“Developing clear disambiguating atmospheric tracers for the presence of liquid water versus magma
oceans is key in our quest of finding potentially habitable worlds amongst the exoplanet population,” they conclude.

 

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Here’s how Helene and other storms dumped a whopping 40 trillion gallons of rain on the South

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More than 40 trillion gallons of rain drenched the Southeast United States in the last week from Hurricane Helene and a run-of-the-mill rainstorm that sloshed in ahead of it — an unheard of amount of water that has stunned experts.

That’s enough to fill the Dallas Cowboys’ stadium 51,000 times, or Lake Tahoe just once. If it was concentrated just on the state of North Carolina that much water would be 3.5 feet deep (more than 1 meter). It’s enough to fill more than 60 million Olympic-size swimming pools.

“That’s an astronomical amount of precipitation,” said Ed Clark, head of the National Oceanic and Atmospheric Administration’s National Water Center in Tuscaloosa, Alabama. “I have not seen something in my 25 years of working at the weather service that is this geographically large of an extent and the sheer volume of water that fell from the sky.”

The flood damage from the rain is apocalyptic, meteorologists said. More than 100 people are dead, according to officials.

Private meteorologist Ryan Maue, a former NOAA chief scientist, calculated the amount of rain, using precipitation measurements made in 2.5-mile-by-2.5 mile grids as measured by satellites and ground observations. He came up with 40 trillion gallons through Sunday for the eastern United States, with 20 trillion gallons of that hitting just Georgia, Tennessee, the Carolinas and Florida from Hurricane Helene.

Clark did the calculations independently and said the 40 trillion gallon figure (151 trillion liters) is about right and, if anything, conservative. Maue said maybe 1 to 2 trillion more gallons of rain had fallen, much if it in Virginia, since his calculations.

Clark, who spends much of his work on issues of shrinking western water supplies, said to put the amount of rain in perspective, it’s more than twice the combined amount of water stored by two key Colorado River basin reservoirs: Lake Powell and Lake Mead.

Several meteorologists said this was a combination of two, maybe three storm systems. Before Helene struck, rain had fallen heavily for days because a low pressure system had “cut off” from the jet stream — which moves weather systems along west to east — and stalled over the Southeast. That funneled plenty of warm water from the Gulf of Mexico. And a storm that fell just short of named status parked along North Carolina’s Atlantic coast, dumping as much as 20 inches of rain, said North Carolina state climatologist Kathie Dello.

Then add Helene, one of the largest storms in the last couple decades and one that held plenty of rain because it was young and moved fast before it hit the Appalachians, said University of Albany hurricane expert Kristen Corbosiero.

“It was not just a perfect storm, but it was a combination of multiple storms that that led to the enormous amount of rain,” Maue said. “That collected at high elevation, we’re talking 3,000 to 6000 feet. And when you drop trillions of gallons on a mountain, that has to go down.”

The fact that these storms hit the mountains made everything worse, and not just because of runoff. The interaction between the mountains and the storm systems wrings more moisture out of the air, Clark, Maue and Corbosiero said.

North Carolina weather officials said their top measurement total was 31.33 inches in the tiny town of Busick. Mount Mitchell also got more than 2 feet of rainfall.

Before 2017’s Hurricane Harvey, “I said to our colleagues, you know, I never thought in my career that we would measure rainfall in feet,” Clark said. “And after Harvey, Florence, the more isolated events in eastern Kentucky, portions of South Dakota. We’re seeing events year in and year out where we are measuring rainfall in feet.”

Storms are getting wetter as the climate change s, said Corbosiero and Dello. A basic law of physics says the air holds nearly 4% more moisture for every degree Fahrenheit warmer (7% for every degree Celsius) and the world has warmed more than 2 degrees (1.2 degrees Celsius) since pre-industrial times.

Corbosiero said meteorologists are vigorously debating how much of Helene is due to worsening climate change and how much is random.

For Dello, the “fingerprints of climate change” were clear.

“We’ve seen tropical storm impacts in western North Carolina. But these storms are wetter and these storms are warmer. And there would have been a time when a tropical storm would have been heading toward North Carolina and would have caused some rain and some damage, but not apocalyptic destruction. ”

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Follow AP’s climate coverage at https://apnews.com/hub/climate

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Follow Seth Borenstein on Twitter at @borenbears

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Associated Press climate and environmental coverage receives support from several private foundations. See more about AP’s climate initiative here. The AP is solely responsible for all content.

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‘Big Sam’: Paleontologists unearth giant skull of Pachyrhinosaurus in Alberta

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It’s a dinosaur that roamed Alberta’s badlands more than 70 million years ago, sporting a big, bumpy, bony head the size of a baby elephant.

On Wednesday, paleontologists near Grande Prairie pulled its 272-kilogram skull from the ground.

They call it “Big Sam.”

The adult Pachyrhinosaurus is the second plant-eating dinosaur to be unearthed from a dense bonebed belonging to a herd that died together on the edge of a valley that now sits 450 kilometres northwest of Edmonton.

It didn’t die alone.

“We have hundreds of juvenile bones in the bonebed, so we know that there are many babies and some adults among all of the big adults,” Emily Bamforth, a paleontologist with the nearby Philip J. Currie Dinosaur Museum, said in an interview on the way to the dig site.

She described the horned Pachyrhinosaurus as “the smaller, older cousin of the triceratops.”

“This species of dinosaur is endemic to the Grand Prairie area, so it’s found here and nowhere else in the world. They are … kind of about the size of an Indian elephant and a rhino,” she added.

The head alone, she said, is about the size of a baby elephant.

The discovery was a long time coming.

The bonebed was first discovered by a high school teacher out for a walk about 50 years ago. It took the teacher a decade to get anyone from southern Alberta to come to take a look.

“At the time, sort of in the ’70s and ’80s, paleontology in northern Alberta was virtually unknown,” said Bamforth.

When paleontogists eventually got to the site, Bamforth said, they learned “it’s actually one of the densest dinosaur bonebeds in North America.”

“It contains about 100 to 300 bones per square metre,” she said.

Paleontologists have been at the site sporadically ever since, combing through bones belonging to turtles, dinosaurs and lizards. Sixteen years ago, they discovered a large skull of an approximately 30-year-old Pachyrhinosaurus, which is now at the museum.

About a year ago, they found the second adult: Big Sam.

Bamforth said both dinosaurs are believed to have been the elders in the herd.

“Their distinguishing feature is that, instead of having a horn on their nose like a triceratops, they had this big, bony bump called a boss. And they have big, bony bumps over their eyes as well,” she said.

“It makes them look a little strange. It’s the one dinosaur that if you find it, it’s the only possible thing it can be.”

The genders of the two adults are unknown.

Bamforth said the extraction was difficult because Big Sam was intertwined in a cluster of about 300 other bones.

The skull was found upside down, “as if the animal was lying on its back,” but was well preserved, she said.

She said the excavation process involved putting plaster on the skull and wooden planks around if for stability. From there, it was lifted out — very carefully — with a crane, and was to be shipped on a trolley to the museum for study.

“I have extracted skulls in the past. This is probably the biggest one I’ve ever done though,” said Bamforth.

“It’s pretty exciting.”

This report by The Canadian Press was first published Sept. 25, 2024.

The Canadian Press. All rights reserved.

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The ancient jar smashed by a 4-year-old is back on display at an Israeli museum after repair

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TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.

Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.

Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.

The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.

The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.

It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.

Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.

Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.

Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.

Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.

Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.

The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”

The Canadian Press. All rights reserved.

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