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Home / Science / Titan’s atmosphere has all the ingredients for life. But not life as we know it

Titan’s atmosphere has all the ingredients for life. But not life as we know it



Using the Atacama Large Millimeter / submillimeter Array (ALMA), a team of scientists have identified a mysterious molecule in Titan’s atmosphere. It is called xyclopropenylidene (C3H2), a simple carbon-based compound that has never been seen in the atmosphere before. According to the group’s study published above Astronomical JournalThis molecule may be a precursor to more complex compounds that may indicate life on Titan.

Similarly, Dr. Catherine Neish of the University of Western Ontario’s Institute of Earth and Space Exploration (Western Space) and her colleagues in the European Space Agency (ESA) have found that Titan Other chemicals can be raw materials for the exotic life forms. In their research, appeared in Astronomy & Astrophysics, they present the Cassini mission data revealing the composition of the craters on the surface of Titan.

The international team responsible for the discovery of cyclopropenylidene includes researchers from NASA’s Solar System Exploration Division (SSED), the Association of Universities Space Research (USRA), Institute of Astronomy and Astrophysics in Taipei, and many universities. They are led by Conor Nixon and Dr. Alexander Thelen, a planetary scientist and postdoctoral fellow at NASA’s Goddard Space Flight Center (respectively).

This true color Titan image, taken by the Cassini spacecraft, shows the thick and translucent atmosphere of the moon.  Image: By NASA - http://photojournal.jpl.nasa.gov/catalog/PIA14602, Public Domain, https://commons.wikimedia.org/w/index.php?curid=44822294
This true color Titan image, taken by the Cassini spacecraft, shows the thick and translucent atmosphere of the moon. Vendor: NASA

The team used the ALMA observatory to study Titan in 2016. While sifting through the light markers that ALMA had collected, they found that the spectrum indicated a strange chemical fingerprint. After searching through a database of all known molecular light markers, Nixon identified it as xyclopropenylidene (C3H2). Nixon said in a NASA press release:

“When I realized I was working on cyclopropenylidene, my first thought was, ‘Well, this is really surprising. Titan is unique in our solar system. It has been shown to be a treasure trove of new molecules ”.

In the past, scientists discovered C3H2 in pockets across the galaxy, but only in interstellar gas and dust clouds (ISM). In these regions, conditions are too cold and diffuse to facilitate chemical reactions. In any other medium, xyclopropenylidene easily reacts with other molecules to form various chemical compounds.

However, Nixon and his colleagues were able to detect small amounts of cyclopropenylidene around Titan because they were examining the upper layers of the moon’s atmosphere, where there are less other gases for C3H2 to interact with. How this could have happened to Saturn’s largest moon and no other celestial body in the Solar System remains a mystery. But what it does may be even more important.

Cyclopropenylidene in Titan and in the molecular cloud
Until now, discoveries of cyclopropenylidene were confined to the pockets of air and dust in interstellar space. Vendor: Conor Nixon / NASA Goddard Space Flight Center

Although C3H2 is not involved in modern biological reactions here on Earth, it is an example of what is known as a “closed loop molecule”, which is important because they form the spinal loops for nucleobases of DNA and RNA – these two compounds are the fundamental building blocks of life as we know it.

Michael Malaska, who worked in the pharmaceutical industry, decided to change car builders and become a JPL planetary scientist to be able to study objects like Titan. As he explained, the search for molecules like C3H2 is essential to setting up seeing the big picture about Titan:

“It’s a very strange little molecule, so it won’t be the kind of class you learn about high school chemistry or even college chemistry. Down here on Earth, it’s not going to be what you’ll come across… Every little piece and part you can explore can help you put together the great puzzle of all that is going on there. “

Another closed-loop molecule found in Titan’s atmosphere is benzene (C6H6). Until now, benzene was thought to be the smallest of the cyclic hydrocarbon molecules that could exist in the atmosphere – but that state clearly belonged to cyclopropenylidene. Furthermore, the cyclical nature of both molecules gave the researchers an additional chemical branch that could allow the formation of DNA and RNA.

In any case, the role of these compounds will certainly be that Dragonfly mission possible to investigate. The mission is scheduled to kick off in 2027 and includes a propeller lander drone that will explore Titan’s atmosphere and surface to learn more about its rich pre-biological environment. and its organic chemistry. Among other things, this mission is responsible for answering whether Titan can actually support life on its surface and in its methane lakes.

This has been a point of speculation and curiosity for decades, since Journey 1 and 2 Space probes flew over the Saturn system in 1980 and 1981. When that happened Cassini-Huygens with the mission arriving around Saturn in 2004, what it observed only attracted more scientists. What these missions discovered was that although very cold, Titan clearly resembled Earth in some ways.

For starters, it has a dense atmosphere (four times thicker than Earth) with mostly nitrogen. No other planet or moon in the Solar System can make that claim! Plus, it has a methane cycle that is very similar to the Earth’s water cycle, complete with surface lakes and rivers, evaporation, clouds and precipitation. There is even evidence that it may have an ocean of salty water below the surface.

But most interesting are active organic processes, where methane and other hydrocarbons in Titan’s atmosphere interact with solar radiation, disrupting and releasing a possible organic chemical lattice. leading to pre-biological surface conditions. This is exactly what pushed Titan to the top of the list of potential destinations for NASA missions looking for past and present life in the Solar System.

Saturn’s moon Titan concept of a lake at the north pole illustrates protruding contours and rampart-like features, such as what NASA’s Cassini spacecraft sees around Winnipeg Lacus of the moon. Image provider: NASA / JPL-Caltech

As Rosaly Lopes, a senior research scientist and Titan expert at NASA’s Jet Propulsion Laboratory (JPL), summarizes:

“We are trying to find out if Titan is viable or not. So we want to know which compounds from the atmosphere go to the surface, and then, can that material be able to penetrate the ice crust to the ocean below, because we think the ocean is a place where living conditions exist. “

Another point of interest that makes Titan an intriguing research target is the possibility that the molecules that may lie on Titan’s surface may resemble those that form the life-masses on Earth. About 3.8 billion to 2.5 billion years ago (during the Achean Eon period), Earth was a very different place where the atmosphere was made up mainly of nitrogen, CO.2, methane and steam.

Essentially, the conditions on Earth during this period were thought to be similar to those on Titan today. Melissa Trainer, NASA’s Goddard astronomer, is the Dragonfly mission’s lead investigator and lead investigator of a key tool it will use to analyze the composition of the Titan’s surface. As she points out:

“We think of Titan as a real-life laboratory where we can see chemistry similar to that of the ancient Earth when life was going on here. We will look for molecules larger than C3H2But we need to know what’s going on in the atmosphere to understand the chemical reactions that lead to complex organic molecules to form and rain down on the surface.

https://dragonfly.jhuapl.edu/What-Is-Dragonfly/img/df-screencap-1.png
Artist’s impression of the Dragonfly mission on the Titan’s surface. Credit: JHUAPL

Similarly, assistant professor Catherine Neish and her colleagues at ESA also found something very interesting when studying Titan’s surface. Normally, atmospheric processes bury Titan’s surface ice beneath a thick layer of organic matter, especially around the dry equator of the moon. This material acts like sand and leads to dust storms and sand dunes formation when high winds occur.

Fortunately, there are places where surface ice can be seen through and scientists can study it and learn more about its composition. For example, higher latitudes on Titan have more rainfall, leading to surface currents that erode sand. In addition, there are also craters created by objects hitting the surface, revealing a relatively new layer of ice in the titanium crust. As Neish explains:

“It is wild. There is no other place like Titan in the solar system. There’s more sand on Titan in each area than anywhere else. And Titan has weather. It is not different from the Earth in that way. It’s just that the ingredients are all wrong. It has methane rain and streams cut through the surface and organic sand is blown around. It is still very active as it is here on Earth. “

Unfortunately, it is difficult to see the surface clearly because of Titan’s dense atmosphere. But after checking the data obtained by CassiniNeish and her colleagues’ infrared and visible mapping spectroscopy (VIMS) was able to clearly see three craters in Titan’s equatorial region and its mid-latitude region.

Artist’s concept of a dust storm on Titan. Credit: IPGP / Labex UnivEarthS / University Paris Diderot – C. Epitalon & S. Rodriguez

What they found was that the equatorial craters of Selk, Ksa, Guabonito and the crater in Santorini Facula seem entirely composed of dark organic matter. Middle latitudes craters of Afekan, Soi, Forseti, Menrva and Sinlap have been found enriched with water ice and organic material. They were also able to determine that none of the ice they observed was ammonia (NH3) or frozen CO2 (also known as “dry ice”).

This is in line with Titan models showing it to be a dynamic environment with its surface-shaping active processes. The combination of water and organic matter could also mean there were ancient ecosystems frozen on the bottom of colliding craters. As part of the science and engineering group that oversees this mission, Neish’s findings here may inform the Dragonfly mission and where it will seek viable evidence of life.

It also illustrates how to find possible extraterrestrial life that is slowly moving beyond Mars to include positions in the outer Solar System. Neish says:

“More and more I think, we are seeing the wrong parallels between life and Mars. The recent discoveries of Venus and all the new things we are learning about it were once an oceanic world is a game changer. Ultimately, everyone is saying that, in the process of searching for life in the universe, we really need to focus on more places, and not just on Mars. And that includes NASA sending the Dragonfly mission to Titan. “

The next few decades promise to be a very exciting time to explore the space (and the fans of it!). In addition to going back to the Moon, establishing a sustainable presence there and sending the first crew members to Mars, we’ll also send our robot explorers to investigate Europa, Ganymede, and Titan with hope to find life there.

In doing so, we will finally be able to shed light on how life began in our Solar System, and how and where it could exist across the Universe!

Read more: NASA, WesternU


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