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Air & Space (USA): life flourished on Mars in the past

© flickr.com, SpaceX

In his new work, published in the International Journal of Astrobiology, Vincenzo Rizzo from the National Research Center in the Italian city of Cosenza asks a provocative question. Why do many scientists do not want to use geological methods to identify biological processes on Mars, while on Earth these methods are widely used?

He points to one case that took place in Germany in 1908. Then a scientist named Ernst Kalkowsky suggested that multilayer hummocks, columns and sheet-like sedimentary rocks, called stromatolites, are biological in nature. Contemporaries did not believe him. But it was later proved that Kalkovsky was right when it became known for what reason stromatolites are formed. And they arise due to the fact that biofilms consisting of cyanobacteria and other microorganisms capture sedimentary deposits. Stromatolites are the oldest evidence of life on Earth since they are at least 3.5 billion years old and still exist in some remote regions, such as Shark Bay in Australia.

In his work, Rizzo follows in the footsteps of Kalkovsky, analyzing images taken on Mars by the rovers Spirit, Optitude, and Curiosity. These images indicate the presence of biological macrostructures such as stromatolites. He believes that unless a different, non-biological explanation is found, removed by the Mars rovers should be considered Martian stromatolites. Rizzo demonstrates a large number of structures that are strikingly similar to terrestrial stromatolites.

In principle, I am very doubtful of evidence that is based only on external resemblance or morphology, since the human brain tends to see or fill with familiar images, even where they do not exist. But Rizzo in his analysis is not limited to appearance. He made me realize that if (and this is big if) stromatolites really existed at an early stage in the life of Mars, then they looked exactly like the samples that he found in the images taken by all-terrain vehicles.

Here comes to mind the famous saying of Carl Sagan (Carl Sagan):

“Unusual statements require unusual evidence.”

For each structure that appears as a result of biological processes, there is a certain geochemical or physical process that imitates it. Some of these processes may not be known to us, because they occur on other planets such as Mars. On the other hand, we now know more about Mars than in the past. We know that at the early stage of the history of this planet, there were lakes, and possibly oceans, including in the Gale Crater, where he made his photographs of Curiosity. Organic matter was found in that place, and we know that pieces of rock can get from Earth to Mars (and vice versa), and also that microbes can survive such a journey. What, then, is a more “unusual” statement? What on Mars during the early usable period were such life forms that were similar to terrestrial ones, and which produced similar biogenic structures? Or that Mars has always been and remains a dead planet?

© CC BY-SA 4.0, Alicejmichel

One way or another, the bar for applications for the discovery of life on Mars (both in the past and in the present) must be set very high. Even on Earth, it is sometimes difficult to decide whether a particular structure is the result of biological processes. Now we have more opportunities to explore Mars, but we still cannot do what we do on Earth all the time: go out into the street with a magnifying glass or other device, and study this or that mysterious feature.

If in the future we conduct an isotopic analysis of the structures discovered by Rizzo, which are similar to stromatolites, we will be able to obtain new evidence or refutation of their biological origin (life prefers lighter isotopes that we can use for verification). But I have suspicions that this hypothesis will face the same fate as Kalkovsky’s assumption. The final verdict will be issued much later, most likely when Mars will begin to investigate people who arrived there. And I hope they prove him right.

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ESPRESSO spectrograph confirms the existence of an earth-like planet near Proxima Centauri

The surface of Proxima b through the eyes of the artist ESO / M. Kornmesser

The ESPRESSO spectrograph confirmed the existence of the earth-like exoplanet Proxima b in the star closest to the Sun. Additional observations made by the tool made it possible to clarify its mass, as well as register a second signal, which theoretically can be explained by the presence of another planet. Accepted for publication at Astronomy & Astrophysics, the preprint is available at arXiv.org.

In 2016, astronomers reported the discovery of the planet at the red dwarf Proxima Centauri, the closest star to Earth, located about 4.2 light-years from Earth. The celestial body revolves around the star with a period of 11.2 days and is in the habitable zone – this means that the conditions on its surface allow the existence of liquid water. 

The discovery of Proxima b was one of the most important milestones in exoplanetary astronomy in recent years, but the limited accuracy of the available measurements of radial velocity and the complexity of the simulation required confirmation of the existence of an earth-like planet.

An international group of astronomers used the new-generation spectrograph ESPRESSO, which is part of the VLT complex, to measure the radial velocity of a star with an accuracy of 30 centimeters per second. The data obtained were three times more accurate than the data of the HARPS spectrograph, an instrument of the same type, but of the previous generation, with the help of which the discovery was made. Combining ESPRESSO observations with past measurements showed that the mass of Proxima b is not less than 1.17 earth masses, which is less than the previous estimate of 1.27 earth masses.

In addition, scientists recorded an additional signal repeating with a period of 5.5 days, which so far they have not been able to explain. Hypothetically, it can come from the second planet: if the assumption is true, then its minimum mass is less than a third of the earth, and it is located at a distance of 0.03 astronomical units from Proxima Centauri (one astronomical unit is equal to the average distance from the Earth to the Sun).

In the past, researchers suspected the existence of another planet in the system – this time the super-earth, on which the year lasts about five years. It is five and a half times more massive than the Earth and may have rings similar to the rings of Saturn, but this discovery has not yet been confirmed.

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It’s time to worry. Planets switched to retrograde motion

© NASA / Tunc Tezel

In May, Venus, Saturn and Jupiter become retrograde – they change the direction of motion in the celestial sphere. Previously, it was considered a bad omen. In fact, in the solar system there is only one real retrograde – Venus. But the discovery of retrograde exoplanets was a complete surprise.

Copernicus explained everything

Even in ancient times, people noticed that planets moving in the heavens sometimes behave strangely, loop. Most of the year they follow from west to east (if they are farther from the Sun than the Earth) and suddenly turn around, back down. The moment when this happens is called standing.In 1514, Nicolaus Copernicus proved that the Earth is not the center of the universe, but together with other planets revolves around the Sun. 

Each celestial body has its own orbit, and the retrograde movement that is visible to us is the result of their superposition. For example, Mars approaches the Earth every two years as closely as possible and, overtaking it, draws an s-shaped loop in the sky.

© NASA / Tunc Tezel

The path of Mars in the celestial sphere in the period from July 2005 to February 2006. It goes from west to east and at the moment of approaching the Earth makes a loop. For a couple of months his movement seems retrograde to us.

Venus and Uranus versus all

All planets in relation to the Earth for a short time move backward, but this is only an appearance. Real retrogrades do not physically rotate like the rest. In the solar system, it is only Venus. If we were above the north pole of Venus, we would see that it rotates clockwise around its axis. Earth and other planets are against.It is believed that planets form together with a star from one protoplanetary disk. In theory, their orbits should lie in the same plane, and the directions of rotation in the orbit and around the axis should coincide. Why Venus is not like this is not yet clear. 

Although scientists note its strong similarity with the Earth – these planets are even called twins. One of the explanations is that the processes occurring in the bowels and atmosphere have slowed the rotation of Venus so much that it stopped at some point, and then began to spin in another direction.

The distant ice giant Uranus also looks like a retrograde. It lies on its side relative to the plane of its orbit, and pecks down the north pole, which makes Uranus seem to rotate clockwise. But if you put it normally, it will become normal. Scientists believe that billions of years ago, Uranus collided with a large cosmic body and turned over in space. Another hypothesis is that in the past the planet had a massive system of rings that caused resonance, rocked it and deployed.

General rules apply to planetary moons. For example, the Earth rotates counterclockwise, and so does the Moon around the Earth. But one of the 13 moons of Neptune – Triton – is “against the coat.” So, scientists conclude, Triton did not belong to Neptune, was an independent small body, until Neptune captured it from the Kuiper belt. By the way, Pluto, similar in composition to Triton, is also retrograde. In part, this contributed to its transfer to the category of dwarf planets.

© Illustration by RIA Novosti. NASA / JPLRetrograde motion of Triton. This is the only major satellite in the solar system that moves in orbit against the course of its planet.

Anomalies of hot jupiters

This is what our system is completely devoid of – planets that would move in orbits against the rotation of the Sun. For a long time, astronomers believed that this should be everywhere. But in 2009, they discovered the first exoplanet with a retrograde orbit at the star WASP-17 in the constellation Scorpio.WASP-17 b is the largest and least dense exoplanet known. Such gas giants are called hot jupiters.

Its retrograde intrigues scientists. Smadar Naoz from the Center for Interdisciplinary Research in Astrophysics at Northwestern University ( USA ) proposed a possible mechanism: the mutual influence of giant planets during migration closer to a star or a brown dwarf. But its implementation requires the coincidence of too many conditions, and this is unlikely. Nevertheless, the astrophysicist put forward a bold hypothesis that such retrograde jupiters are not uncommon – a quarter among those observed. However, the existence of the hot Jupiters themselves is still waiting for its explanation.

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A space object that changes the concept of the Universe is discovered: An unthinkable ancient galaxy

Photo: NRAO / AUI / NSF / S. Dagnello

Scientists at the Institute for Astronomy of the Max Planck Society in the UK announced the discovery of the oldest massive galaxy DLA0817g, which arose just 1.5 billion years after the Big Bang. It has a disk, which can change astronomers’ ideas about the mechanisms of galaxy formation. An article by astronomers is published in the journal Nature.

Researchers discovered the galaxy using the ALMA (Atacama Large Millimeter Array) radio telescope complex. This ancient object was named Wolf Disc – in honor of the astronomer Arthur Wolf. It has become the farthest spinning-disk galaxy of all detected so far, and its cosmological redshift is 4.26. 

The light from it flew 12.2 billion years, but due to the expansion of the Universe, the galaxy is currently at a distance of 24.4 billion light years. The rotation occurs at a speed of 272 kilometers per second, which is comparable to the rotation speed of the Milky Way.

According to modern models, massive galaxies are formed from the mergers of smaller mass galaxies and clusters of hot gas. These collisions prevent the formation of disks characteristic of the Universe of this age. 

Therefore, the existence of the Wolf Disc will force astronomers to reconsider the mechanisms of the appearance of such space objects. DLA0817g probably accumulated cold gas, but the question of how he managed to maintain a stable disk with such a large mass remains open.

Scientists also found that the star formation rate in the Wolf Disk is ten times higher than the star formation rate in the Milky Way. According to astronomers, he was one of the most productive galaxies in the early Universe.

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