2020
May
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Salty Mars puddles no place for life

On the surface of the Red Planet, normal bodies of water cannot exist for long periods of time under today’s conditions. It’s possible, however, that very salty “puddles” or reservoirs of liquid (“brines” in technical language) could remain stable on or just below the surface for some amount of time, especially during the Mars spring and summer months, when ice deposits thaw. Whether these puddles are suitable for life as we know it, however, remains questionable.

In 2018, reports sparked headlines that these brines might have conditions that are friendly to life after all. One factor speaking for this was that oxygen would dissolve very well in the brines under the conditions prevalent on Mars. While our neighboring planet’s atmosphere has only 0.145 percent oxygen (Earth: 21 percent), the brines might be relatively rich in oxygen and could therefore provide a foundation for life for microorganisms.

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Life in a hydrogen-rich atmosphere

The exoplanet K2-18b, about 124 light-years from Earth, is a kind of mini-Neptune, as astronomers discovered this past year. It is seven to ten times heavier than Earth and its radius is 2.7 times larger. K2-18b orbits its host star, a red dwarf, once every 33 days. Thus, it is located in its star’s habitable zone.

For astronomers, however, it has one other special noteworthy feature: hydrogen, helium, and water vapor have been detected in its atmosphere. In the media, K2-18b has even been described as “Earth 2.0,” which it very definitively is not. The researchers who studied it in 2019 described it at the time as “very likely more harmful to life” than Earth.

Hydrogen in the atmosphere is not generally considered especially friendly to life: it is very reactive; any available oxygen molecules would be immediately converted to water, thus ruling out any sort of breathing as we know it. But does that mean we should write off K2-18b as a candidate for extraterrestrial life? That would be a premature conclusion according to scientists. As an experiment, they tested how life might function in a hydrogen-rich atmosphere in a laboratory.

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Silent Sun: The phenomenon of our quiet star

The Sun is rather quiet. That’s the premise of my novel “Silent Sun.” But now researchers at the Max Planck Institute for Solar System Research (MPS) in Göttingen, Germany have also proved it with a systematic comparison published in Science. In such analyses, of course, it is important to make sure you are not comparing apples with oranges. Red dwarfs, for example, are considered much more active. But even among the class of yellow dwarfs like the Sun, there can be big differences.

Therefore, the researchers selected candidate stars that were similar to the Sun in terms of important characteristics. In addition to surface temperature, age, and proportion of heavy elements, another characteristic was rotational velocity. “The speed at which a star rotates about its own axis is a crucial variable,” says Sami Solanki, director at MPS and co-author of the study.

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