A distant planet shows traces of life

Mars' lost carbon finally discovered by NASA rover

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Coffee Table Science
April 20, 2025

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Smell plays a role in women's friend selection

Heterosexual women partly use scent to assess friendship potential, often deciding within minutes quickly, a new study has found. Pheromones subtly influence attraction in many species. Fish and mice studies showed a preference for mates with different major histocompatibility complex (MHC) genes (important for immunity and transplant compatibility), possibly to maintain genetic diversity and avoid inbreeding. 

Wedekind's "sweaty T-shirt" study on MHC and human mate preference found women preferred the scent of men with dissimilar MHCs. The findings spurred numerous "smelly T-shirt" studies and "pheromone parties." 

This new research explored smell in platonic bonds, using "diplomatic" odor (including environmental scents) instead of strictly "natural" odor. The "Speed-Friending" study with 40 women had four phases: headshots, visual friendship ratings, 12-hour T-shirt wear, and friendship ratings based on smell (twice) and a 4-minute live interaction. 

Smell-based friendship ratings strongly correlated with in-person evaluations and predicted changes after live interaction, suggesting a learned element. Acknowledging their focus on young heterosexual women, the authors proposed future studies on broader age ranges, different developmental stages, male friendships, and cross-cultural scent influences on friendship.

The insights were published in the journal Scientific Reports.

Mars' lost carbon finally discovered by NASA rover

NASA’s Curiosity rover on Mars has unearthed a hidden deposit of carbon-rich minerals providing initial proof of carbon cycle on the Red Planet. The find also hints at its inactive pace which might have caused the planet’s environmental shift. 

Once a world with plentiful water and a warm climate sustained by a thick CO2 atmosphere, Mars is now a cold, dry desert with a very thin atmosphere. According to the recently found evidence, carbon must be locked up in the carbonate minerals. 

Curiosity rover found these carbonates in the form of siderite in the Gale crater, on a mountain within the former lakebed. siderite. Curiosity drilled four rock samples across an 89-meter area, and researchers analyzed their composition using the rover's onboard chemistry lab. 

Siderite found in sulfate layers likely formed as Mars dried via water-rock reactions and evaporation. The samples contained 5-10% siderite. If similar amounts exist in other Martian sulfates, we'd be much closer to understanding the fate of the lost atmospheric CO2.

The rocks' iron oxyhydroxides, from siderite dissolving in acidic water, suggest a carbon cycle with some atmospheric return. But unlike Earth's billions-year-stable cycle, Mars' surface rocks trapped much more carbon than they released. 

The lack of CO2 return explains Mars' past habitability and its subsequent uninhabitability. The siderite finding offers a strong explanation for the missing carbonate and a thick early Martian atmosphere supporting liquid water. 

The insights were published in Science.

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Human eye "hacked" to perceive a novel color, 'olo'

Scientists developed a method to "hijack" the eye, allowing five people to see "olo," a "blue-green of unprecedented saturation" beyond natural vision. The aim is to achieve full programmable control of every light-sensing cell in the retina. Achieving this precise control over the retina could lead to entirely new methods for investigating how vision works. 

Human eyes have rods (night vision) and cones (color vision: red/L, green/M, blue/S). Color perception relies on brain's interpretation of cone activation patterns. Since M cones' sensitivity overlaps with L and S, they're normally activated together. Scientists wondered about isolating M cone activation. 

The "Oz" retinal stimulation technique, inspired by "Wizard of Oz" glasses, started as M cone research but became a precise vision study method. It uses detailed retinal maps made from stitched videos and AO-OCT to identify L, M, and S cones' sensitivity. Experiments then used targeted laser microdoses to activate specific cones (like only M), with real-time eye tracking for accuracy.

Isolating M cone stimulation produced 'olo' (color map 0, 1, 0: no L/S, full M). Participants viewed 'olo' in visuals. 'Olo' is described as a highly saturated green, making even laser light seem pale in comparison. Current Oz limitations include: indirect viewing using peripheral vision (central cones too small for precise targeting), difficulty applying to the sharp-vision fovea, and requiring a fixed gaze because only a small retinal area was mapped. Free gaze would need extensive mapping and extremely precise eye movement tracking for laser delivery.

Researchers are looking into Oz to study/treat color blindness, simulate tetrachromacy (increased color sensitivity), and model eye diseases. Scientists could use Oz to mimic eye diseases to better understand vision loss and potentially simulate full color vision for the color-blind by compensating for missing receptors. Introducing new retinal stimulation patterns might even allow them to learn to perceive new colors.

The findings were published in the journal Science Advances.

A distant planet shows traces of life

While studying an exoplanet,  astronomers reported detecting an unexpected atmospheric gas – dimethyl sulfide, mainly produced by life on Earth. In April 2024, JWST observed K2-18b's star for six hours as the planet transited, capturing starlight filtered through its atmosphere revealing molecular fingerprints. Comparing the fingerprints to 20 possible molecules, astronomers found the best match was a gas indicative of life on Earth.

Read how astronomers find a habitable exoplanet on Coffee Table Science.

Located a relatively short 120 light-years away from Earth, K2-18b is the first planet of the 18th system found by the Kepler (K2) mission, hence its "b" designation. Despite limited knowledge, K2-18b is un-Earthlike – 8 times more massive, 18 times larger, and only half as dense, indicating a lot of water or a vast, low-density atmosphere. Astronomers see K2-18b as either a mini-Neptune or a rocky gas dwarf with a massive hydrogen atmosphere.

For the first time, the James Webb Space Telescope's short-wavelength infrared camera examined starlight passing through K2-18b's atmosphere. It detected carbon monoxide and methane while finding a lack of water vapor in the upper layers. 

The data also showed a weak signal possibly indicating dimethyl sulfide (DMS), a gas mainly produced by Earth's marine algae, with few non-biological origins. This makes its potential detection on an ocean-bearing planet, making it an exciting prospect for life. 

New data show a stronger, signal attributed to DMS or a similar molecule. In the future, K2-18b is set to become a significant object of study for the James Webb Space Telescope. 

The findings were published in The Astrophysical Journal Letters.

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