Earth Sky | Extraterrestrial life? The possibilities are increasing

Extraterrestrial life: a world of increasing possibilities

Is there life outside Earth? Whether elsewhere in our solar system, or far from the outer planets, this question remains unanswered. But the answers may come close. Several recent discoveries seem to support the possibility of extraterrestrial life. The past week or so has been a great example, with the announcements of several tantalizing new results. Among them are the ocean of Saturn’s moon Enceladus that’s becoming more habitable than previously thought, super-Earth exoplanets that may be more habitable than Earth, and new evidence of early wet and warm Mars, including many more lakes than ever before. Initially thought, the ocean is ancient. .

The participating researchers have published several new peer-reviewed research papers in PNAS, ScienceDirect, Nature Astronomy (1), Nature Astronomy (2), Nature Geoscience, and Science Advances.

Enceladus Ocean

First, Enceladus. Like Jupiter’s moon Europa, this small moon of Saturn has an ocean of water beneath the Earth’s surface. This in and of itself makes it interesting. But in addition to that, NASA’s Cassini spacecraft flew through some plumes of water vapor that were blasted into space from the moon’s south polar region. They are believed to have originated from the ocean itself. Cassini found some puzzling components in the plumes, including water vapor, ice particles, salts, methane, and organic compounds. There is also evidence of active hydrothermal vents on the ocean floor. All this makes this ocean a potential habitat for life.

However, one thing was missing: phosphorous. Cassini hasn’t found anything, but now a new study from researchers at the Southwest Research Institute (SwRI) shows that it’s likely there. If so, then Enceladus’ ocean contains all the ingredients necessary for life (at least as we know it on Earth). Co-author Christopher Glenn stated:

Enceladus is one of the main targets of humanity’s search for life in our solar system. In the years since NASA’s Cassini spacecraft visited the Saturn system, we have been repeatedly surprised by the discoveries made possible by the data collected. What we have learned is that the shaft contains almost all the basic requirements for life as we know it. While the vital element phosphorous has not been directly identified, our team discovered evidence of its availability in the ocean beneath the moon’s icy crust.

Phosphorous is essential for the formation of DNA, RNA, energy-carrying molecules, cell membranes, bones, teeth, and the sea microbiome of plankton.

Phosphorous geochemistry simulation

The SwRI team performed thermodynamic and kinetic modeling that simulates the geochemistry of phosphorous based on insights from Cassini about the ocean floor system on Enceladus. They have developed the most detailed geochemical model to date of how seafloor minerals in Enceladus’ oceans are melting. Modeling predicted that the phosphate minerals would be extraordinarily soluble in the ocean. Glenn added:

Basic geochemistry has an elegant simplicity that makes the presence of dissolved phosphorous inevitable, reaching levels close to or higher than those found in modern seawater on Earth. What this means for astrobiology is that we can be more confident than before that Enceladus’ ocean is habitable.

Super-Earths may be more habitable than Earth

Astronomer Chris Impey published another interesting article on Conversation on September 23, 2022. In it, he explained that superplanets – exoplanets larger and more massive than Earth but smaller and less massive than Neptune – might not only be habitable, but Even more habitable from our planet.

It is also common, and is now estimated to include about a third of the known exoplanets. As Embi wrote:

Based on current projections, about a third of exoplanets are super-Earths, making them the most common type of exoplanet in the Milky Way. The closest is only six light years from Earth. You might even say that our solar system is unusual because it does not have a planet with a mass between Earth and Neptune.

Habitable planets?

And super-Earths—at least some of them—might be more habitable than Earth. Imbe wrote:

Researchers have come up with a list of traits that make a planet so conducive to life. Larger planets are more likely to be geologically active, a feature that scientists believe will boost biological evolution. So, the most habitable planet would have nearly twice the mass of Earth and be between 20% and 30% larger by volume. It would also have oceans shallow enough for light to stimulate life all the way to the sea floor and an average temperature of 77 degrees Fahrenheit (25 degrees Celsius).

It would have a thicker atmosphere than the Earth’s, which would act as an insulating cover. Finally, such a planet would orbit a star older than the Sun to give life longer to evolve, and would have a strong magnetic field protecting against cosmic radiation. Scientists believe that these traits combined will make the planet habitable.

By definition, a super-Earth possesses many of the attributes of a super-habitable planet. So far, astronomers have discovered twenty super-Earths that are, if not the best of all possible worlds, more habitable than Earth in theory.

The Webb Telescope will be able to take a closer look at some of these alien worlds and analyze their atmospheres for possible chemical signs of life known as biosignatures.

Mars warmer and wetter early?

For decades, scientists have debated whether Mars was warmer and wetter a few billion years ago. Or was it cold and humid? Or cold and mostly dry? A new press release from the SETI Institute outlines new evidence that Mars was born with a wet and dense atmosphere. This would have allowed warm oceans to exist for millions of years.

Researchers have developed the first-ever model of the evolution of the Martian atmosphere linking high temperatures from the formation of Mars in a molten state to the formation of the first oceans and atmosphere. The results indicated that, just as on Earth, water vapor is concentrated in the lower atmosphere and condenses in the form of clouds. SETI Research Scientist Kaveh Pahlevan said:

We think we penned an overlooked chapter in the earliest history of Mars in the immediate aftermath of the planet’s formation. To explain the data, the atmosphere of primitive Mars must have been very dense (about 1,000 times as dense as the modern atmosphere) and composed primarily of molecular hydrogen (H2). This finding is important because H2 is known to be a potent greenhouse gas in dense environments. This dense atmosphere would have produced a strong greenhouse effect, allowing very early warm-to-hot water oceans to settle on Mars for millions of years until H2 is gradually lost to space. For this reason, we conclude that – sometime before the Earth itself formed – Mars was born wet.

Mars: the land of lakes?

Another study, conducted by researchers in Hong Kong, also supports the previously wetter planet Mars. The study suggests that scientists underestimated how many lakes there were on Mars. According to Joseph Michalsky, a geologist at the University of Hong Kong:

We know of approximately 500 ancient lakes deposited on Mars, but nearly all of the lakes we know are larger than 100 square kilometres. But on Earth, 70 percent of lakes are smaller than this size, and they occur in cold environments where glaciers have retreated. These small lakes on Mars are difficult to identify by satellite remote sensing, but there are likely many small lakes. It is possible that at least 70% of Martian lakes have yet to be discovered.

According to the new paper, most of the already known Martian lakes date back about 3.5 to 4 billion years. It may also have only lasted from 10,000 to 100,000 years. Some may be quite muddy and murky, due to the low gravity and fine-grained soil. This could be a challenge for any putative photosynthetic organisms (using photosynthesis) in those lakes. But, as Michalsky also noted, other lakes would have been deeper and longer-lived, with hydrothermal systems capable of supporting life.

Further exploration is needed to find evidence of these and other smaller lakes. However, if it does exist, that supports the possibility that life, even if only microbial, could have been found on ancient Mars.

More Evidence for an Ancient Ocean on Mars

Finally, Space.com reports that China’s Zhurong rover has found new evidence of an ancient ocean on Mars. Zhurong explores the plains of ancient Utopia Planitia. If Mars, as some scholars say, had an ocean, it was likely that Utopia Planitia, a huge basin, was a part of it. According to the China National Space Administration (CNSA), the rover has returned 1,480 gigabytes of raw data so far. Some of this data supports the ocean hypothesis.

Scientists report the discovery of wet minerals in Peel. A hard crust is a hard mineral layer over the soil that is usually formed due to the evaporation of groundwater. As reported by Space.com, the researchers said this is evidence of “significant liquid water activity” in the area sometime in the past billion years.

In addition, Zhurong found evidence of “high durability and low friction parameters” in the soil. This may be due to erosion from wind, water, or both.

A previous PNAS study from last January also supports the existence of an ancient polar ocean in the northern hemisphere.

Extraterrestrial life: where will we find it first?

While none of these results are new fix There is extraterrestrial life, it shows that the possibilities are increasing. While we still only know about life on Earth, there may be multiple scenarios – in our solar system and beyond – in which organisms could arise and evolve. Where will we find the first definitive guide? In the ancient rocks of Mars? In the waters of the ocean moon in the outer solar system? On a distant exoplanet? The possibilities may be endless!

Bottom line: Several new reports and discoveries, including five new papers, support the possibility of extraterrestrial life. Are we close to finding alien life?

Sources:

An abundance of phosphorous is expected for possible life in the vicinity of Enceladus

The primordial origin of deuterium enrichment in the Martian hydrosphere

(Preprint) A primitive atmospheric origin of deuterium enrichment in the Martian hydrosphere

Geological diversity and microbiological potential of lakes on Mars

Geomorphic contexts and scientific focus of the Zhurong landing site on Mars

Surface Characteristics of the Zhurong Mars Rover Crossing in Utopia Planitia

Zhurong reveals recent water activities at Utopia Planitia, Mars

Across:

Conversation

SwRI

SETI Institute

University of Hong Kong

Space.com

CGTN