Tag Archives: Snowball

Exoplanet LHS 1140b in the Habitable Zone: Could it be a Snowball or Waterworld?

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LHS 1140b is the second-closest temperate transiting exoplanet to Earth, with temperatures cold enough for liquid water to exist on its surface.

LHS 1140b could be a completely icy world, like Jupiter's moon Europa (left), or it could be an icy world with a liquid ocean and cloud-like atmosphere (centre). Image courtesy of B. Gougeon / University of Montreal.

LHS 1140 is a cool, low-mass star located about 39 light-years from Earth in the constellation Cetus.

Also known as Gliese 3053, GJ 3053 and 2MASS J00445930-1516166, the star is about one-fifth the size of our Sun and is about 5 billion years old.

LHS 1140 is known to be home to three exoplanets: LHS 1140b, LHS 1140c, and LHS 1140d.

Earlier this year, astronomers reported new mass and radius estimates for LHS 1140b with extraordinary precision, matching estimates for the better-known TRAPPIST-1 planet: 1.7 times the size and 5.6 times the mass of Earth.

One of the key questions about LHS 1140b was whether it was a mini-Neptune-type exoplanet or a super-Earth.

The latter scenario included the possibility of the existence of so-called Hythean worlds with global liquid oceans enveloped in a hydrogen-rich atmosphere, which would show a clear atmospheric signal observable using Webb.

Analysis of Webb's new observations completely rules out the mini-Neptune scenario and provides compelling evidence suggesting that exoplanet LHS 1140b is a super-Earth, possibly with a nitrogen-rich atmosphere.

If confirmed, this result would make LHS 1140b the first temperate planet to show evidence of a secondary atmosphere that formed after the planet's initial formation.

Estimates based on all the accumulated data suggest that LHS 1140b is less dense than expected for a rocky planet with an Earth-like composition, and that 10-20% of its mass may be made up of water.

The discovery indicates that LHS 1140b is a fascinating watery world, possibly similar to a snowball or ice planet, and the planet's expected synchronous rotation means that a region of the planet's surface could always harbor a liquid ocean at its substellar point, facing the system's host star.

Artist's impression of planetary system LHS 1140. Image courtesy of Sci.News.

“Among the currently known temperate exoplanets, LHS 1140b may be the best candidate for future indirect confirmation of the existence of liquid water on the surface of an alien world outside our solar system,” said Charles Cadieux, a doctoral student at the University of Montreal.

“This will be a major milestone in the search for potentially habitable exoplanets.”

Although still preliminary, the presence of a nitrogen-rich atmosphere on LHS 1140b suggests that the planet could retain a significant amount of atmosphere, creating the conditions for liquid water to exist. This finding makes the water-world/snowball scenario the most plausible.

Current models suggest that if LHS 1140b had an Earth-like atmosphere, it would be a snowball planet with a huge bull's-eye shaped ocean about 4,000 km in diameter, equivalent to half the surface area of ​​the Atlantic Ocean.

Surface temperatures in the core of this alien ocean could reach a comfortable 20 degrees Celsius.

LHS 1140b has favorable conditions for a potential atmosphere and liquid water, making it an excellent candidate for future habitability studies.

“The planet provides a unique opportunity to study worlds that could potentially support life, as it is located in the habitable zone of its star and likely has an atmosphere capable of retaining heat and supporting a stable climate,” the astronomers said.

Team paper will be published in Astrophysical Journal Letters.

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Charles Cadieux others2024. Transmission spectroscopy of the habitable zone exoplanet LHS 1140b with JWST/NIRISS. Apu JL,in press; arXiv:2406.15136

Source: www.sci.news

Snowball Earth’s harsh environmental conditions provided a competitive edge for the evolution of multicellular organisms

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Fossil and molecular evidence suggests that complex multicellular organisms arose and proliferated during the Neoproterozoic Era (1-541 million years ago). An extreme glacial period during the Cryogenian Period (720-635 million years ago), an event commonly referred to as Snowball Earth, led to dramatic changes in Earth's climate and oceans. New research suggests that Snowball Earth was an environmental trigger for the proliferation of complex multicellularity across multiple groups of eukaryotic organisms.

Artist's impression of “Snowball Earth.” Image courtesy of NASA.

Solving the mystery of why multicellular organisms emerged could help pinpoint life on other planets and explain the enormous diversity and complexity seen on Earth today, from marine sponges to redwoods to human societies.

The prevailing thinking is that oxygen levels must reach a certain threshold for a single cell to form a multicellular colony.

However, the oxygen story does not fully explain why the multicellular ancestors of animals, plants and fungi emerged simultaneously, or why the transition to multicellularity took more than a billion years.

The new study shows how the specific physical conditions of Snowball Earth, particularly the viscosity of the oceans and the depletion of resources, may have led eukaryotes to become multicellular.

“It seems almost counterintuitive that these extremely harsh conditions – this frozen planet – could actually select for larger, more complex organisms, rather than causing species to become extinct or shrink in size,” said William Crockett, a doctoral student at MIT.

Using scaling theory, Crockett and his colleagues found that a hypothetical ancestor of early animals, reminiscent of swimming algae that fed on prey instead of photosynthesizing, would have grown in size and complexity under Snowball Earth pressures.

In contrast, single-celled organisms that move and feed by diffusion, such as bacteria, will grow small.

“The world changed after Snowball Earth because new life forms emerged on the planet,” said Professor Christopher Kemps of the Santa Fe Institute.

“One of the central questions of evolution is: How did we evolve from nothing on Earth to beings and societies like us? Was it all by chance?”

“We don't think it's luck. There are ways to predict these big changes.”

The study shows how, during the Snowball Earth era, the oceans froze, blocking sunlight and reducing photosynthesis, which resulted in nutrient depletion in the oceans.

Larger organisms that could process more water were more likely to eat enough to survive.

As the glaciers melt, these large creatures could expand even further.

“Our study provides hypotheses about ancestral features to look for in the fossil record,” Crockett said.

of study Published in Proceedings of the Royal Society B.

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William W. Crockett others2024. Snowball Earth's physical constraints drive the evolution of multicellularity. Proc. R. Soc. B 291 (2025): 20232767; doi: 10.1098/rspb.2023.2767

This article is a version of a press release provided by the Santa Fe Institute.

Source: www.sci.news

Study finds that low carbon dioxide emissions from volcanoes may have caused the Sturtian ‘Snowball Earth’ ice age.

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of Sturtian “Snowball Earth” Ice Age (717 million to 661 million years ago) is considered the most extreme icehouse period in Earth’s history. In a new study, geologists from the University of Sydney and the University of Adelaide used plate tectonics modeling to identify the most likely cause of the Staats Ice Age.

Artist’s impression of “Snowball Earth”. Image credit: Oleg Kuznetsov, http://3depix.com / CC BY-SA 4.0.

“Imagine if the Earth almost completely froze over, which is exactly what happened about 700 million years ago,” said lead author Dr. Adriana Dutkiewicz, a researcher at the University of Sydney. .

“The Earth was covered in ice from the poles to the equator, and temperatures plummeted. But what caused this to happen is an open question.”

“We think we have now solved the mystery. Historically, volcanic carbon dioxide emissions have been low, driven by the weathering of large volcanic rock mountains in what is now Canada. It’s a process that absorbs carbon dioxide.”

Named after Charles Sturt, a 19th-century European colonial explorer of central Australia, the Sturtsian Ice Age spanned 717 million to 660 million years, long before dinosaurs and complex plants existed on land. It continued until ten thousand years ago.

“There are many possible causes for the trigger and end of this extreme ice age, but the most mysterious one is why it lasted 57 million years. It’s hard for humans to imagine,” Dr. Dutkiewicz said.

Dr. Dutkiewicz and his colleagues used a plate tectonics model that simultaneously shows the evolution of continents and ocean basins after the breakup of the ancient supercontinent Rodina.

They connected it to a computer model that calculates the outgassing of carbon dioxide from submarine volcanoes along mid-ocean ridges, where plates diverge and new oceanic crust is born.

They soon realized that the beginning of the Starch Ice Age correlated precisely with the lowest ever levels of volcanic carbon dioxide emissions.

Additionally, carbon dioxide flux remained relatively low throughout the ice age.

“At that time, there were no multicellular animals or land plants on Earth,” Dr. Dutkiewicz said.

“Greenhouse gas concentrations in the atmosphere were determined almost entirely by carbon dioxide emitted by volcanoes and by the weathering processes of silicate rocks that consume carbon dioxide.”

“At that time, geology ruled the climate,” said co-author Professor Dietmar Müller, a researcher at the University of Sydney.

“We think the Staats Ice Age began with a double whammy: plate tectonics realigned to minimize volcanic degassing, while at the same time Canada’s continental volcanic belt began to erode, removing carbon dioxide from the atmosphere. Consumed.”

“As a result, atmospheric carbon dioxide has fallen to levels that could begin an ice age. This is estimated to be less than 200 parts per million, less than half of today’s levels.”

The team’s current research raises interesting questions about the long-term future of the planet.

Recent theories suggest that over the next 250 million years, Earth will evolve toward Pangea Ultima, a supercontinent hot enough to wipe out mammals.

However, the Earth is currently on a trajectory where volcanic carbon dioxide emissions decrease as continental collisions increase and plate velocities decrease.

So perhaps Pangea Ultima will snowball again.

“Whatever the future holds, it is important to remember that geological climate changes of the type studied here occur very slowly,” Dr. Dutkiewicz said.

“According to NASA, human-induced climate change is occurring 10 times faster than ever before.”

of study appear in the diary geology.

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Adriana Dutkiewicz other. The period of the Sturtian “Snowball Earth” ice age is associated with unusually low gas emissions at mid-ocean ridges. geology, published online on February 7, 2024. doi: 10.1130/G51669.1

Source: www.sci.news