#Planetary_geology

[phonemantra-blog]

New research shows how comets could be the source of life on planets outside our solar system Scientists theorize that comets may have spread the organic ingredients necessary for the emergence of life on Earth. New research suggests that comets may also deliver these elements to exoplanets. During the formation of the solar system, the Earth was bombarded by asteroids, comets and other space objects. How the planet obtained the water and molecules necessary for life is still controversial, but comets are considered the most likely sources of these substances. [caption id="attachment_83089" align="aligncenter" width="650"] planet[/caption] But if comets could potentially bring the seeds of life to Earth, could they serve a similar function for exoplanets in other parts of the universe? To explore this question, a team of researchers from the Institute of Astronomy at the University of Cambridge developed mathematical models that helped reveal how comets could transfer similar vital elements to other planets in our galaxy. While the study's findings do not yet provide a definitive answer about the presence of life on other planets, they may help narrow the search for exoplanets that may support life. “wandering” from planet to planet, spread life throughout the Universe? “We continue to learn more about the atmospheres of exoplanets, so our goal was to find out whether there were planets where complex organic molecules could also be delivered by comets. It's possible that the molecules that enabled life on Earth were brought in by comets, and the same may be true for planets in other galaxies,” said Richard Enslow, one of the study's authors, who works at the Institute of Astronomy at the University of Cambridge. Over the past decades, scientists have learned more about the prebiotic molecules found in comets. For example, NASA's Stardust mission discovered samples of glycine, an amino acid and building block of proteins, in Comet Wild 2 (81P/Wild), and the European Space Agency's Rosetta mission discovered organic molecules in the coma of Comet Churyumov-Gerasimenko (67P). However, these organic molecules can be destroyed by strong comet impacts on the planet. So Enslow and his colleagues had to find scenarios in which a comet-planet collision occurs slowly enough to preserve the ingredients of life intact. The study, based on simulations, found that the slowest impact velocities occur in solar systems where planets are densely packed. Comets moving through such systems are slowed down by the gravitational influence of the planets. The simulations also showed that conditions for the emergence of life may be suitable on rocky planets orbiting red dwarfs. They are the most common type of star in the galaxy and are of interest to astronomers searching for exoplanets. However, planets in such systems are subject to more frequent high-speed collisions with comets and the likelihood of life appearing there is low, especially if the planets are located at significant distances from each other. “We can identify the types of systems that could be the subject of research to test different models for the origin of life. And this is another way to look at the amazing diversity of life on Earth and look for its analogues on other planets,” Anslow commented.

[wigmund]

From NASA Image of the Day; March 14, 2018:

There's Always Pi!

Craters can tell scientists a lot about the surfaces of planets, moons and other bodies. Just by determining how circular a given crater is – using pi and the crater’s perimeter and area – planetary geologists can reveal clues about how the crater was formed and the surface that was impacted.

Each year across the globe, people celebrate Pi Day. On March 14 (3/14 in the month/day date format, since 3, 1, and 4, or 3.14, are the first three significant digits of π, we sing the praises of this mathematical constant. Here at NASA, whether it's sending spacecraft to other planets, driving rovers on Mars, finding out what planets are made of or how deep alien oceans are, pi takes us far. Here are 18 ways that pi helps us explore space.

Image Credit: NASA

[phonemantra-blog]

New work suggests active tectonics on ancient Venus and that the tectonic state of the planets may change over time A new study confirms that high levels of nitrogen and argon in Venus's atmosphere indicate emissions of gases during tectonic activity billions of years ago. This suggestion could mean that Venus may have been habitable for a long period before some event that changed its conditions. Scientists have long sought to understand why Venus's carbon dioxide-rich atmosphere is 90 times denser than Earth's and contains almost no water vapor, despite the planet's temperature being maintained at 462 degrees Celsius. However, there is a possibility that such conditions were not always like this. Previous studies modeling Venus's geological past have pointed to the possibility of a small ocean of liquid water and a habitable surface early in the first two billion years or so of the planet's early history. [caption id="attachment_77000" align="aligncenter" width="750"] Venus[/caption] Scientists from Brown University used the underlying data to compare Venus's current atmosphere with atmospheres created by a variety of models of long-term thermo-chemical-tectonic evolution. In other words, they tried to establish a correspondence between the current atmosphere of the planet and possible previous scenarios that take into account tectonic changes. “Venus’s existing atmosphere requires gases to be ejected early in its life due to activity similar to plate tectonics. Our results indicate that the atmosphere of Venus is the result of a climate-tectonic transition that lasted at least a billion years, and then transitioned to the current regime of a virtually stationary “stagnant mantle” with reduced rates of gas emissions,” the scientific team notes in their paper. . The concept of a “stagnant mantle” (Stagnant lid) means that the surface of the planet consists of a single plate with limited mobility and gas release into the atmosphere. The study of Venus has given rise to suggestions that planets can change their tectonic state and living conditions The researchers simulated the events that had to happen on the planet for it to reach the state it is in now. Scientists believe that Venus likely had active plate tectonics immediately after its formation, approximately 4.5 billion to 3.5 billion years ago. Based on the proposals in the paper, early tectonic movement, similar to that of the Earth, was limited by both the number of moving plates and the scale of their displacement. However, presumably, some events occurred on Venus that led to a stop in the tectonic movement of plates. Because this work has the potential to change our current understanding of planetary evolution, additional testing of the model's results is necessary. “Up until now, we thought that plate tectonics was in a 'binary state': it either exists or it doesn't. It either existed throughout the entire history of the planet or did not exist at all. In our work, we showed that planets can transition between different states of tectonics. "In addition, the results also indicate that there may be planets transitioning between habitable states and not just viable ones," said study co-author Alexander Evans, assistant professor of earth, environmental and planetary sciences at Brown University. In addition, this work points to the possibility of several ways to interpret the history of the planet. “At the moment, we still adhere to the paradigm where we study their surfaces to understand the history of planets. But we have demonstrated that the atmosphere may be the best tool for understanding the ancient history of planets, which is often not preserved on their surface,” Evans said. Future missions to Venus will help refine the data from this study. NASA's DAVINCI (Deep Atmosphere Venus Investigation of Noble gases, Chemistry and Imaging) mission will provide measurements of gases in the atmosphere of Venus. In turn, the European Space Agency's EnVision probe will probe the planet's dense atmosphere from orbit using high-resolution radar. DAVINCI is scheduled to launch in 2029 and EnVision between 2035 and 2039.