Astronomy

SpaceX plans to launch its huge Starship rocket on Thursday (June 6), provided it clears the required regulatory hurdles.

The Martian surface shows ample evidence of its warm, watery past. Deltas, ancient lakebeds, and dry river channels are plentiful. When the Curiosity rover found organic matter in ancient sediments in the Jezero Crater paleolake, it was tempting to conclude that life created the matter.

However, new research suggests that non-living processes are responsible.

There are three carbon isotopes on Earth: carbon-12 (12C), carbon-13 (13C), and carbon-14 (14C). Earth’s carbon is almost entirely carbon-12. It makes up 99% of the carbon on Earth, with carbon-13 making up the other 1%. (14C is extremely rare and unstable, so it decays into nitrogen-14.)

In 2022, MSL Curiosity took an inventory of organic carbon in sediments at Gale Crater. Organic carbon is usually described as carbon atoms bonded covalently to hydrogen atoms and is the basis for organic molecules. The carbon in organic carbon can be either carbon-12 or carbon-13, and the amounts are important. At Gale Crater, Curiosity found about 200 to 273 parts per million of organic carbon. “This is comparable to or even more than the amount found in rocks in very low-life places on Earth, such as parts of the Atacama Desert in South America, and more than has been detected in Mars meteorites,” said Jennifer Stern, a Space Scientist at NASA’s Goddard Space Flight Center when the results came in.

This is the Stimson sandstone formation in Gale Crater on Mars. This is where the Curiosity Rover drilled the Edinburgh hole and found enriched Carbon 12. Image Credit: NASA/Caltech-JPL/MSSS

This carbon is important evidence in understanding Mars’ history. It can tell scientists about the planet’s atmospheric processes and environmental conditions and even shed light on potential life. In fact, understanding Martian carbon can aid our understanding of habitability and prebiotic chemistry on distant exoplanets. The isotope ratio in this carbon is different than on Earth. It has a lower amount of carbon-13 relative to carbon-12 compared to Earth. Why the discrepancy?

In recent research in Nature Geoscience, a team of researchers tried to understand the difference between Earth’s and Mars’s carbon isotope ratios. The work is titled “Synthesis of 13C-depleted organic matter from CO in a reducing early Martian atmosphere.” The lead author is Yuichiro Ueno, a biogeochemist in the Department of Earth and Planetary Sciences at the Tokyo Institute of Technology.

“Strong 13C depletion in sedimentary organic matter at Gale crater was recently detected by the Curiosity rover,” the authors write. “Although this enigmatic depletion remains debated, if correct, a mechanism to cause such strong 13C depletion is required.” 

The amount of carbon-13 in the Martian sediments is far lower than in Earth’s sediments.

“On measuring the stable isotope ratio between 13C and 12C, the Martian organic matter has a 13C abundance of 0.92% to 0.99% of the carbon that makes it up,” lead author Ueno explained in a press release. “This is extremely low compared to Earth’s sedimentary organic matter, which is about 1.04%, and atmospheric CO2, around 1.07%, both of which are biological remnants and are not similar to the organic matter in meteorites, which is about 1.05%.”

The meteorite data is important because a four billion-year-old Martian meteorite named ALH 84001 is enriched in carbon-13, adding to the enigma of Mars’ carbon. Somehow, carbon-13 became depleted in the intervening billions of years. Solar escape is one possible reason for the carbon-13 depletion, but the authors discount that. There likely wasn’t enough time for enough carbon-13 to escape. “Furthermore, based on geomagnetic observations, early Mars probably had a geomagnetic field before 4?Ga,” the authors write. That field would’ve prevented solar escape.

To determine what’s behind this discrepancy, Ueno and his co-researchers simulated different Martian atmospheric conditions to see what would happen.

Their results show that isotope fractionation by solar UV light is responsible for Mars’ 13C depletion.

This graphic outlines the process that creates atmospheric organic matter that finds its way into the Martian sediments sampled by MSL Curiosity. Image Credit: Ueno et al. 2024.

Carbon-12 and carbon-13 respond differently to UV light. Carbon-12 preferentially absorbs UV, which dissociates it into carbon monoxide that’s depleted in carbon-12. What’s left behind is CO2 enriched with carbon-13.

Scientists have observed this process in the upper atmospheres of Earth and Mars. In Mars’ reducing atmosphere, where oxygen was depleted, the CO2 enriched with carbon-13 would’ve transformed into formaldehyde and possibly methanol. But those compounds didn’t remain stable. In Mars’ early days, the surface temperature was close to the freezing point of water, and it never exceeded about 27 Celsius (80 F.) In that temperature range, the formaldehyde and other compounds could’ve dissolved in water. From there, they gathered in sediments.

But that’s not the end of Mars’ carbon isotope story.

The researchers used models to show that in a Mars atmosphere with a CO2 to CO ratio of 90:10, 20% of the CO2 would have converted to CO, leading to the sedimentary carbon isotope ratio we see today. The remaining atmospheric CO2 would be higher in C-13, and both values are in line with what Curiosity found, and with the ancient Martian meteorite ALH 84001.

This is a plausible scenario that can explain Curiosity’s curious carbon findings.

The team’s study also includes some other important details. For instance, atmospheric CO may not have come solely from photolysis by UV light. Some could have come from volcanic eruptions. And atmospheric CO may not have been the sole source of organics that found their way into the sediments. But either way, the results tell scientists something about Mars’ carbon cycle.

It also tells us to expect to find more organics in Martian sediments in the future.

“If the estimation in this research is correct, there may be an unexpected amount of organic material present in Martian sediments. This suggests that future explorations of Mars might uncover large quantities of organic matter,” said Ueno.

While the research shows us that life needn’t be present to produce these organics, it can’t rule life out. Nobody can, at least not yet.

The research also shows how complex atmospheric chemistry can be and how difficult it can be to draw conclusions from atmospheric studies of exoplanets. The JWST has examined several exoplanet atmospheres and found some interesting results. But there’s so much we don’t know. This research is a reminder that any conclusions are likely premature.

The post Life Probably Played No Role in Mars’ Organic Matter appeared first on Universe Today.

Mice that exercised soon after waking up had stronger and longer bones than those that exercised later in the day  

Mice that exercised soon after waking up had stronger and longer bones than those that exercised later in the day  

India's Agnikul Cosmos successfully launched a test vehicle powered by a homegrown 3D printed rocket engine.

The Chang’e 6 mission is China’s second to touch down on the lunar far side and will retrieve samples for analysis on Earth

This year's U.S. Astronaut Hall of Fame induction ceremony was a reunion of sorts, as honorees David Hilmers and Marsha Ivins took the stage under Atlantis, the shuttle on which they crossed paths.

A small South Pacific fern boasts more than 50 times as many base pairs as the human genome

A rare sighting of a giant pangolin revives hopes for the species' survival in West Africa, despite threats from poaching and deforestation

A rare sighting of a giant pangolin revives hopes for the species' survival in West Africa, despite threats from poaching and deforestation

A Russian military satellite with a "history of unusual maneuvering" was spotted as it approached a satellite in geostationary orbit in April 2024.

"Twisted Tatooine" binary star systems could be a major player in ejecting rogue planets that go on to drift through the Milky Way without a stellar parent to heat or illuminate them.

As we discover more and more exoplanets – and the current total is in excess of 5,200 – we continue to try to learn more about them. Astrobiologists busy themselves analysing their atmospheres searching for anything that provides a sign of life. It is quite conceivable of course that the Universe is teeming with life based on very different chemistry to ours but we often look to life on Earth to know what to look for. On Earth for example, ozone forms through photolysis of molecular oxygen and is an indicator of life. Using the James Webb Space Telescope astronomers are searching stars in the habitable zone of their star for the presence of ozone and how it impacts their climate.

It’s tantalising that 425 of the exoplanets detected so far, exist in their stars habitable zone. It is in this region where the climate on the planet may well be suitable to sustain life. A significant subset of those planets are Earth-like in nature and will therefore have a fairly temperate climate. In addition, they all seem to orbit M-dwarf type stars which means they are likely to be impacted by tidal spin-synchronisation (due to the effects of the tides, one face of the planet may well be kept facing the star). One impact of this is the potential for large contrast in daytime and night-time irradiation which can drive strong convection on the day side of the planet.  

The strong convection can drive winds around the equatorial region that are persistently higher faster than the rotation of the planet. It can also create Rosby Waves which naturally occur in the Earth’s ocean and atmosphere – in any rotating fluids or gas. Together these can control the distribution of chemicals in the atmosphere, in particular ozone. 

In Earth’s atmosphere the presence of molecular oxygen is an indicator of life since it is produced largely from photosynthesis in plants. The molecular oxygen collides with nitrogen in the atmosphere to produce ozone so the presence of the latter is an indicator of biological processes. There is a chance though that the molecular oxygen in exoplanet atmospheres are the result of different ratios of near and far UV that can drive a non-biological build up. 

In a new piece of research reported in a paper by lead author Paolo De Luca and team, they report their findings having leveraged climate model simulations on Proxima Centauri b. The Earth-sized exoplanet orbits the red dwarf star Proxima Centauri, the closest star to our own at a distance of 4,.2 light years. 

An artist’s conception of a violent flare erupting from the red dwarf star Proxima Centauri. Such flares can obliterate atmospheres of nearby planets. Credit: NRAO/S. Dagnello.

They report that the analysis of atmospheres of tidally locked Earth-like exoplanets received a massive boost as a result of the development of the James Webb Telescope. The team reveal that their climate modelling (including the use of interactive ozone) globally increases temperature in the stratosphere. This in turn induces regional variations of surface temperature and also reduces the temperature contrast between day and night side. 

Whilst the team have not been able to identify life on exoplanets, that was not their intention. What they have achieved is the ability to understand the exoplanet atmospheres using the James Webb Space Telescope, some of the processes that lead to atmospheric ozone and the impacts on temperatures. 

Source : The impact of Ozone on Earth-like exoplanet climate dynamics: the case of Proxima Centauri b

The post What Impact Does Ozone Have on an Exoplanet? appeared first on Universe Today.

Strange solids called temporal metamaterials finally make it possible to investigate the controversial idea of quantum friction – and push special relativity to its limits

Strange solids called temporal metamaterials finally make it possible to investigate the controversial idea of quantum friction – and push special relativity to its limits

China Chang’e 6 mission has landed on the Moon and is now set to perform another first: a sample return from the lunar farside.

The post Whirlwind Chang’e 6 Mission Collects Lunar Samples, Heads Back Home appeared first on Sky & Telescope.

A rare fossil skull provides strong evidence that the Dromornithidae, an extinct group of Australian flightless birds, were related to geese and ducks

A rare fossil skull provides strong evidence that the Dromornithidae, an extinct group of Australian flightless birds, were related to geese and ducks

Anthony Fauci, who led the National Institute of Allergy and Infectious Diseases early in the COVID pandemic, is facing a congressional committee about questionable e-mails from agency officials

China's Chang'e-6 lunar mission has carried out a successful far side touchdown and is already busily gathering specimens for send-off to Earth.