Astronomy

Making hydrogen from seawater can be tricky because the salt is corrosive and the process can create toxic chlorine gas – new electrodes can split ocean water to make the clean fuel more easily

Making hydrogen from seawater can be tricky because the salt is corrosive and the process can create toxic chlorine gas – new electrodes can split ocean water to make the clean fuel more easily

Photosynthesis changed Earth in powerful ways. When photosynthetic organisms appeared, it led to the Great Oxygenation Event. That allowed multicellular life to evolve and resulted in the ozone layer. Life could venture onto land, protected from the Sun’s intense ultraviolet radiation.

But Earth’s photosynthetic organisms evolved under the Sun’s specific illumination. How would plants do under other stars?

Our Sun is a G-type star, sometimes called a yellow dwarf. It seems like a normal star to us, but yellow dwarfs aren’t that common. Only about 7% to 8% of stars in the Milky Way are G-type stars. When it comes to understanding habitability on exoplanets, we need to understand the more plentiful types of stars.

Some scientists propose that K-dwarf stars are the most optimal host stars for habitable exoplanets. They’re between about 50% and 80% as massive as G-type stars, are more abundant and have stable luminosities for billions of years longer than Sun-like stars. The Sun will be stable on the main sequence for about 10 billion years, while K-type stars can be stable for up to 70 billion years. Despite this, much exoplanet habitability research focuses on M-dwarfs, or red dwarfs, which may actually be far more inhospitable to life because of flaring and tidal locking.

In a new study, a trio of researchers simulated the light output from a K-dwarf star and grew two photosynthetic organisms in those conditions to see how they responded. The research article is “Observation of significant photosynthesis in garden cress and cyanobacteria under simulated illumination from a K dwarf star.” It’s published in the International Journal of Astrobiology, and the lead author is Iva Vilovi?, a PhD student in the Astrobiology Research Group at the Technical University of Berlin.

These figures from the article show the spectra for both the Sun and a K-dwarf star, and the simulated spectra for both. Image Credit: Vilovi? et al. 2024.

Garden cress, whose Latin name is Lepidium sativum, is a common garden green used in salads, soups, and sandwiches. It’s an adaptable plant that grows rapidly. The cyanobacterium Chroococcidiopsis is an extremophile known for lying dormant for 13 million years and remaining viable. It can resist radiation, desiccation, and extreme temperatures and is of interest in astrobiology.

We expect photosynthesis to play a role in astrobiology. Starlight provides the energy for organisms to synthesize organic compounds. In order to understand photosynthesis in astrobiology, we need to understand how other stars could power photosynthesis. “Therefore, understanding any planet in the context of its stellar environment is an essential step in assessing its habitability,” the authors write.

Astronomers search for Earth-like planets around Sun-like stars because that’s the only life we know of. They also pay special attention to M-dwarfs because they’re so plentiful and are known to host many rocky exoplanets in their habitable zones. Scientists have demonstrated that photosynthetic organisms from Earth can grow under simulated M-dwarf light. But M-dwarf habitability faces a whole host of potential barriers.

Artist’s impression of a flaring red dwarf star orbited by an exoplanet. Red dwarfs can flare violently, which could make planets in their habitable zones unable to support life. Planets in their habitable zones are also often tidally locked, which is another barrier to habitability. Credit: NASA, ESA, and G. Bacon (STScI)

In this work, the researchers focused on K-dwarfs. They lack the magnetic activity that appears to generate extremely powerful flaring on M-dwarfs, flaring so powerful that it could sterilize planets in their liquid-water habitable zone. The habitable zones around K-dwarfs are also far enough away that planets wouldn’t be tidally locked, another potential barrier to habitability that affects M-dwarfs. K-dwarfs also become habitable sooner in their lives than M-dwarfs due to their rapidly weakening FUV and X-ray fluxes.

“All things combined, K dwarfs can be considered the ‘Goldilocks stars’ in the search for potentially life-bearing planets,” the authors write.

This table from the research article shows the conditions that the researchers recreated in their study. Image Credit: Vilovi? et al. 2024.

The trio of researchers exposed watercress seedlings to three different light regimes: sunlight, K-dwarf light, and no light. Visually, the solar and K-dwarf samples were similar, though most of the time, the seeds sprouted a day or two earlier than under solar light. The K-dwarf sample also had marginally larger leaf surface area.

The researchers grew garden cress (Lepidium sativum) on a sand substrate with one hundred initial seedlings under Solar (effective temperature 5800 K), K dwarf (effective temperature 4300 K) and dark conditions. This image shows the visual results for selected days. Garden cress under K dwarf radiation sprouts sooner relative to Solar and dark conditions. Image Credit: Vilovi? et al. 2024.

After seven days, a side view of the samples showed that height and stem elongation were different. Under the K-dwarf lighting, the watercress grew taller.

The watercress grew taller under K-dwarf lighting than under Solar conditions. Image Credit: Vilovi? et al. 2024.

The researchers also measured water content and dry mass. Under K-dwarf conditions, the watercress had slightly higher water content, while the dry content was lower compared to solar conditions.

These figures show the water content and dry content for all three garden cress samples. Image Credit: Vilovi? et al. 2024.

The researchers also tested the photosynthetic efficiency and found no significant difference between the solar and K-dwarf samples.

The hardy extremophile Cyanobacterium Chroococcidiopsis sp. CCMEE 029 is at the other end of the spectrum from the quick-growing garden cress. It’s a survivor that can withstand long periods of dormancy and extreme growing conditions. The researchers also cultivated it under Solar, K-dwarf and dark conditions.

They measured the average integrated density (IntD) of the cyanobacterium, which is an indicator of culture growth. They found that the K-dwarf sample exhibited higher values than the solar sample, but the differences were not considered significant. Predictably, “Cyanobacteria under constant dark conditions failed to exhibit significantly measurable IntD,” the authors write in their paper.

This figure from the research article shows incremental ratios and integrated densities of the cyanobacterium on selected days under Solar, K dwarf and dark conditions. Though the integrated density was higher under K-dwarf conditions, the difference isn’t significant, according to the researchers. Image Credit: Vilovi? et al. 2024.

They point out that their study didn’t replicate natural conditions completely. Sunlight intensity changes throughout the day, but they didn’t include that in their study. “Sunlight intensity on Earth varies throughout the day, with peak intensities occurring during the central hours. This variation is crucial for plants to adapt and respond to changing light conditions, including the activation of non-photochemical quenching (NPQ) to mitigate the effects of excess light,” they write. NPQ helps plants cope with periods of excess light, meaning light above what it can photosynthesize, by dissipating it as heat.

“Understanding the effects of K-dwarf radiation on photosynthesis and growth is of foremost importance not only for the assessment of its viability for phototrophic organisms but also for the interpretation of atmospheric biosignatures outside of the Solar System,” the authors explain. Other research in this area has focused on M-dwarfs, and this trio of researchers say that to the best of their knowledge, theirs is the first to look at photosynthesis and K-dwarfs.

“These results can bring us closer to addressing which stellar environments could be the optimal candidates in the search for habitable worlds,” the authors write. “These findings not only highlight the coping mechanisms of photosynthetic organisms to modified radiation environments but also they imply the principal habitability of exoplanets orbiting K dwarf stars.”

The post Plants Would Still Grow Well Under Alien Skies appeared first on Universe Today.

Europe's Mars Sample Fetch Rover showcased its sample-picking skills in field tests for the first time this month.

On September 15th, 2024, the Polaris Dawn crew returned to Earth after spending five days in orbit. The mission was the first of three planned for the Polaris program, a private space project to advance human spaceflight capabilities and raise funds and awareness for charitable causes. The mission’s Dragon spacecraft safely splashed down off the coast of Florida at 3:36:54 a.m. EDT (12:36:54 p.m. PDT). Once their spacecraft was retrieved, the crew was flown to the Kennedy Space Center to see their families and undergo medical examinations before traveling to Houston to complete more of the mission’s studies.

The mission accomplished several objectives, including flying higher than any previous crewed mission since the Apollo Era – 1,408 km (875 mi) above the Earth’s surface, or three times the altitude of the International Space Station (ISS). The mission passed through the Van Allen Radiation Belt to learn more about the effects of space radiation on human physiology. For starters, the mission included the first-ever commercial spacewalk, performed by mission commander Jared Isaacman when the spacecraft was 700 km (435 mi) above Earth.

This feat also tested SpaceX’s new Extravehicular Activity Spacesuit (EVA), designed for long-duration spaceflight and operations on the lunar and Martian surface. Other experiments included Starlink’s laser-based communications system, which is essential for future missions to the Moon, Mars, and beyond. This consisted of the crew sending signals between optical links on the Dragon spacecraft and Starlink satellites. The crew also carried out 36 other science experiments, in collaboration with 31 global institutions, designed to advance human health and space exploration.

The mission also featured a special reading of Kisses from Space, written by Anna Menon (Polaris Dawn’s mission specialist and medical officer) and Keri Vasek. The event was live-streamed and showed Menon sharing her book with her family and many patients at St. Jude Children’s Research Hospital – one of the charitable organizations supported by the Polaris Program. The mission also had a “music moment,” where mission specialist Sarah Gillis played “Rey’s Theme” on the violin from The Force Awakens composed by John Williams.

The recording was back to Earth via Starlink, where it was accompanied by professional and youth musicians from around the world through a series of pre-recorded orchestra sessions. The combined footage was used to create the video “Harmony of Resilience” in support of St. Jude Children’s Research Hospital and El Sistema USA, a charity dedicated to providing access to music education for all children. Additional updates about the mission and crew post-return will continue to be available via Polaris’ official X account, Instagram, and their website. 

The second flight in the Polaris Program will see another crewed Dragon spacecraft launching to orbit and conducting additional experiments to advance human spaceflight, in-space communications, and scientific experiments. The launch date for this mission is currently TBD. The third mission (also TBD) will be the first crewed spaceflight using SpaceX’s Starship and Superheavy launch system.

Further Reading: Polaris Program

The post The Polaris Dawn Crew is Back on Earth appeared first on Universe Today.

The Europa Clipper will determine whether Jupiter’s icy moon has the right conditions for life as we know it.

As someone that has always lived in the UK countryside I am no stranger to the glory of a dark star-filled sky. Sadly 60% of the world’s population has already lost access to the night sky thanks to light pollution. Across Europe and the US that number climbs to nearer 80%. A team of researchers want to try and track the growth of light pollution and to that end have developed an inexpensive sensor made from “off-the-shelf” parts. Their hope is that people around the world will build and install these sensors to share their data enabling them to track the spread of light pollution. If you’ve got technical skills, this could be a fun project.

Astronomers the world over are all too familiar with the scourge of light pollution. It’s one of the main reasons observatories tend to be located in the middle of nowhere. Of course the night sky is illuminated by natural light from the stars and Moon but also zodiacal light and aurora can shed their own mystical light on our sky. Light pollution doesn’t refer to these natural wonders, instead it refers to the excessive or misdirected artificial light from human activity. 

Urban sprawl and accompanying light pollution is an issue for both astronomers and fireflies. This view shows the light dome from the city of Duluth, Minn. 20 miles north of town. It erases the dark skies. Credit: Bob King

Light pollution not only effects astronomers but it disrupts ecosystems, wildlife and even human health. It typically comes from streetlights, building lighting, advertising and even car headlights. It generally creates a nasty orange or white glow that hangs over towns and cities obscuring the beauty of the universe. It also interferes with with the behaviour of nocturnal animals, has a negative impact on human sleep cycles and can lead to health issues like insomnia or stress. There are suitable ways external lighting can be controlled and its impact minimised but we need to get people to actually want to make that change. 

An annotated light pollution map for Nebraska. Credit: Dave Dickinson/The Light Pollution Atlas.

That’s the dream of the team behind the FreeDSM device and the Gaia4Sustaniability project. Their aim is to provide an easy to use piece of hardware and software which is reliable and will be able to measure night sky brightness caused by light pollution. The framework will be able to calculate the excess light pollution which is in excess of natural sky brightness to inform public, non-scientific stakeholders and the science community about the spread of light pollution.

Using hardware that is readily available the device is relatively cheap to build coming in at less than $65 USD (around £50 GBP.) It is based around the Osram TSL2591 sensor with two diodes.  One of them takes sky brightness measurements in the infrared and the other in the full visible spectrum. It then samples the brightness every minute while it also captures humidity and temperature. Looking at the relatively comprehensive instructions it looks like anyone with modest DIY skills will be able to build this. 

The device is an excellent step forward toward analysing the state of light pollution across the planet. It uses data from the Gaia satellite to greatly enhance the accuracy of the light pollution measurements. It does require legions of groups or individuals to build and install a device however. Hopefully it will appeal to the several thousands of fellow geeks out there   to pick up their screwdriver and soldering iron to make the dream of turning the tide on light pollution a reality.

If you want to have a go for yourself then you can learn more about the project here and find the instructions to build your own sensor here

Source : FreeDSM and the Gaia4Sustaniability project: a light pollution meter based on IoT technologies

The post Building a Worldwide Map of Light Pollution appeared first on Universe Today.

SpaceX fired up the engines of its sixth Starship vehicle on Wednesday (Sept. 18) to gear up for a test flight that's probably still several months away.

Nearly imperceptible quantum flickers used to limit how precisely we could detect the way space-time ripples, but squeezing the laser light used in detectors overcomes this and doubles the number of gravitational waves we can see

Nearly imperceptible quantum flickers used to limit how precisely we could detect the way space-time ripples, but squeezing the laser light used in detectors overcomes this and doubles the number of gravitational waves we can see

The average surface temperature varied more widely and was even hotter than previously thought during much of the past 500 million years, according to the most rigorous study so far

The average surface temperature varied more widely and was even hotter than previously thought during much of the past 500 million years, according to the most rigorous study so far

An exclusive interview with "Apollo 13: Survival" director Peter Middleton about his documentary full of archival footage and interviews.

Three scientists are honored for developing a class of blockbuster weight-loss drugs. Is a Nobel prize on the way?

The Sun is midway through its life of fusion. It’s about five billion years old, and though its life is far from over, it will undergo some pronounced changes as it ages. Over the next billion years, the Sun will continue to brighten.

That means things will change here on Earth.

As the Sun goes about its business fusing helium into hydrogen, the ratio of hydrogen to helium in its core changes. Over time, the core slowly becomes more enriched in helium. As helium accumulates in its core, the core’s density increases, meaning protons are more closely packed together. That creates a situation where the Sun can fuse hydrogen more efficiently. After a chain reaction of processes and cause and effect, the end result is that the Sun’s luminosity increases. The Sun’s luminosity has already increased by about 30% since its formation, and the brightening will continue.

Any increase in the Sun’s luminosity can have a pronounced effect on Earth. Environmental cycles like the carbon, nitrogen, and phosphorous cycles sustain Earth’s biosphere. As the Sun becomes brighter, it will affect these cycles, including the carbonate-silicate cycle, which moderates the accumulation of carbon dioxide (CO2) in the planet’s atmosphere.

This schematic shows the relationship between the different physical and chemical processes that make up the carbonate-silicate cycle. In the upper panel, the specific processes are identified, and in the lower panel, the feedbacks associated are shown; green arrows indicate positive coupling, while yellow arrows indicate negative coupling. Image Credit: By Gretashum – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=79674633

Scientists think that over the next billion years, the brightening Sun will disrupt this cycle, leading to declining CO2 levels. Plants rely on CO2 and the levels are expected to plummet, which means that complex land life would end in the next billion years.

It’s a bleak prognosis, but new research suggests it might not happen.

The new research is “Substantial extension of the lifetime of the terrestrial biosphere,” and it’s been accepted for publication in the Planetary Science Journal. It’s in pre-print now, and the lead author is R.J. Graham, a postdoctoral researcher in the Department of Geophysical Sciences at the University of Chicago.

“Approximately one billion years (Gyr) in the future, as the Sun brightens, Earth’s carbonate-silicate cycle is expected to drive CO2 below the minimum level required by vascular land plants, eliminating most macroscopic land life,” the authors write.

As stars like our Sun age, they become brighter and warmer. Image Credit: ESO/L. Calçada

As the Sun brightens and warms the Earth’s surface, scientists expect the carbonate-silicate cycle to draw more CO2 out of the atmosphere because of carbonate-silicate weathering and carbonate burial. Rainwater is enriched with atmospheric carbon, which reacts with silicate rocks and breaks them down. The products of the chemical reactions that break them down find their way to the ocean floor, where they form carbonate minerals. As these minerals are buried, they effectively remove carbon from the atmosphere.

Normally, the cycle acts as Earth’s natural thermostat. However, higher temperatures make the reactions more efficient, meaning the carbonate-silicate cycle will remove more CO2 from the atmosphere. That’s what led scientists to conclude that the CO2 will become so low that planet life will perish. However, the authors examined these ideas and found that it may not quite work out that way.

“Here, we couple global-mean models of temperature- and CO2-dependent plant productivity for C3 and C4 plants, silicate weathering, and climate to re-examine the time remaining for terrestrial plants,” they write. C3 and C4 plants are two main plant groups that are classified based on how they perform photosynthesis and absorb carbon. They’re relevant because they respond differently to higher temperatures.

The researchers say recent data shows that the carbonate-silicate cycle isn’t as temperature-dependent as previously thought. Instead, it’s only weakly temperature-dependent and more strongly CO2-dependent. In that case, “we find that the interplay between climate, productivity, and weathering causes the future luminosity-driven CO2 decrease to slow and temporarily reverse, averting plant CO2 starvation,” they explain.

Instead of a one billion-year outlook for Earth’s plant life, the researchers say atmospheric CO2 levels will mean plants have another 1.6-1.86 billion years. When plants can no longer survive, it won’t be because of plummeting CO2 levels. Instead of CO2 starvation, it’ll be because of what scientists call the moist greenhouse transition.

When that transition happens, a planet’s atmosphere becomes saturated with water vapour as the planet warms. Since water vapour is a potent greenhouse gas, it creates a feedback loop of increased warming. Eventually, it’s simply too hot for plants to survive. The consequences don’t end there. As the Earth’s upper atmosphere becomes more saturated with water vapour, UV energy splits water apart, and the hydrogen drifts off into space. In this situation, there’s a gradual and irreversible loss of water into space.

According to the authors, Earth won’t experience this transition for between about 1.6 and 1.86 billion years.

This astronaut photograph shows the sky over the Amazon Basin during the rainy season. Image Credit: NASA

“We show that recent data indicating weakly temperature-dependent silicate weathering lead to the prediction that biosphere death results from overheating, not CO2 starvation,” the authors write. “These findings suggest that the future lifespan of Earth’s complex biosphere may be nearly twice as long as previously thought.”

These results also affect our understanding of exoplanet habitability. It has to do with what are called ‘hard steps’ in the appearance and evolution of life. The hard steps model says that certain evolutionary transitions were difficult and unlikely to happen twice. Some examples are the appearance of multicellular organisms and the Cambrian explosion.

But if Earth’s biosphere has a much longer lifespan than thought, that affects the hard steps model.

“A longer future lifespan for the complex biosphere may also provide weak statistical evidence that there were fewer “hard steps” in the evolution of intelligent life than previously estimated and that the origin of life was not one of those hard steps,” the authors conclude.

If that’s the case, then exoplanet habitability could be less rare than thought.

The post Life Might Thrive on the Surface of Earth for an Extra Billion Years appeared first on Universe Today.

The European Space Agency's (ESA) Jupiter Icy Moons Explorer (JUICE) mission photographed the Earth, moon and Uranus as it heads toward Venus for a gravity assist next year.

A long-awaited calculation of the W boson’s mass agrees with theory, contradicting a previous anomaly that had raised the possibility of new physics beyond the Standard Model

Genetic testing on samples collected during the earliest days of the covid-19 outbreak suggests it is likely that the virus spread from animals to humans at the Huanan seafood market

Genetic testing on samples collected during the earliest days of the covid-19 outbreak suggests it is likely that the virus spread from animals to humans at the Huanan seafood market

SpaceX's new Starlink satellites are so radio noisy that they could blind radio astronomy observatories to the universe's most intriguing phenomena, scientists say.