Plants will still grow under alien skies” suggests resilience and adaptability in life. It implies that nature can thrive in diverse environments, even those that are unfamiliar or challenging. This idea can evoke themes of exploration, survival, and the interconnectedness of life across different worlds. Would you like to explore this concept further, perhaps in a story or a poem?

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

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.

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

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.

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.

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

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

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

Alien life could take many different forms, but one possibility is captivating scientists: alien “plants”. What would they look like? And how could we find them?

On the Orion arm of the Milky Way galaxy, around 93 million miles (150 million kilometres) from the yellow dwarf star it orbits, is a medium-sized rocky planet. At the edge of a vast southern ocean, are the gently lapping waters of a hot-pink lake. With snow-white, crystalline shores, and more than 38 times the salt concentration of pickled olives, among its sole inhabitants are a kind of obscure life with a striking purple hue. These primitive microorganisms are decidedly alien-like: not quite bacteria, but not exactly like anything else either, they are able to thrive in conditions that seem utterly inhospitable.

Over the last three decades, astronomers have identified 5,528 planets outside our own solar system – a medley of weird worlds, ranging from one so dark, it’s trapped in an eternal night (TrES-2 b), to a poltergeist planet that orbits an undead star (PSR B1257+12 b). And in the not-too-distant future, astronomers are confident that – if there is indeed life beyond Earth – they’ll be able to spot the unmistakable signature of extraterrestrial photosynthesis

Alien plants are expected to be every bit as peculiar as you would imagine: forests of black trees under skies with multiple suns; growths of alien shrubs that all lean in one direction, amid a permanent sunset; carnivorous undergrowth that can swallow up other alien life-forms whole

On Earth, the vast majority of life – by weight, at least – has run with the first option. It’s been estimated that out of the 550 gigatonnes of carbon bound up in living organisms today, 450 gigatonnes are found in vegetation. What if most life in the Universe is photosynthetic? Is it possible that, in fact, our quest for intelligent civilisations has been misguided – and we should have been looking for flora, not fauna, all along?

Though plants look obviously green to the human eye, they have another characteristic that is, in fact, more striking

Another sign of life, as the Galileo spacecraft looked upon planet Earth, was a particular pigment found widely distributed across its surface. That was chlorophyll – again, Sagan had detected signs of vegetation. However, it didn’t appear as you might expect. Though plants look obviously green to the human eye, they have another characteristic that is, in fact, more striking – and easier to spot from space. This is the way they absorb a lot of red light, but not infrared. “Plants are very highly reflective in the near infrared,” says Kiang. Light in this band of the spectrum just isn’t as “delicious” to vegetation – it prefers shorter wavelengths. This rapid change in the wavelengths it absorbs is known as the “red edge”.

One way to find plants on alien planets is to simply copy this experiment, and search for a “red edge” on their surfaces. But it might not always be that straightforward. It’s thought that land plants evolved around 500 million to 725 million years ago, so the Earth has only been smothered with green vegetation for around a ninth of its history. For the rest of the time, there either was no life or it had different reflective characteristics.

Maybe my students, before they retire, might actually have the opportunity to directly image possibly habitable planets – Nancy Kiang

Many people think of plants as nice-looking greens. Essential for clean air, yes, but simple organisms. A step change in research is shaking up the way scientists think about plants: they are far more complex and more like us than you might imagine. This blossoming field of science is too delightful to do it justice in one or two stories. exploring scientific studies that challenge the way you view plantlife.

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