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A first: Methane ice has never been made on Earth before in space conditions.
We see methane (CH4) here on earth as a very powerful greenhouse gas. But did you know that it is abundant in other parts of our solar system? For example, in addition to hydrogen and helium, Neptune and Uranus mainly contain methane gas. And on Titan, a moon of Saturn, it rains liquid methane. But methane can also be found outside of our solar system. In fact, in interstellar space, methane ice is one of the ten most common forms of ice.
Experiment
But how exactly does methane ice originate in that interstellar space? Scientists had ideas about this. But thanks to the work, the resistance in the Leiden Observatory’s astrophysics laboratory, we now know quite accurately. In that lab, the researchers mimicked the conditions in interstellar space and then watched how methane ice sees daylight under those conditions.
Methane is a fairly simple hydrocarbon and consists of one carbon atom and four hydrogen atoms. Methane ice is supposed to be created step by step in space. First CH is formed (one carbon atom binds to a hydrogen atom), then another hydrogen atom (CH2) is added, then another (CH3), all these molecules that like to react more, until the fourth Hydrogen atom results in the formation of stable methane (CH4). In the gas phase, this process is slow because the densities in space are very low. However, it was hypothesized that things can go faster in one particle of icy dust, because several particles freeze together in this area. Additionally, a frozen powder particle can absorb the energy released during chemical reactions, making the chance of a formed molecule falling apart considerably less. The researchers tested this hypothesis by colliding hydrogen and carbon atoms in their laboratory on an icy surface, at a temperature of -263 degrees Celsius and in an ultra-high vacuum.
Danna Qasim with the complex installation that can simulate conditions like those of interstellar space.
Pleasantly surprised
And yes, methane ice was created. “We were pleased to see that methane ice could be formed by adding hydrogen atoms to a carbon atom,” said researcher Danna Qasim. Scientias.nl. “And we were pleasantly surprised to see that you can make even more methane ice cream when you add water (H2O). This is entirely in line with conclusions based on astronomical observations, which show that methane and water ice occur together in dust particles in space. “
From the interstellar cloud to Titan’s atmosphere
The methane ice that Qasim and his colleagues made was created in extreme conditions similar to those seen in space before new stars and planets formed. “The purpose of laboratory astrophysical research is to obtain qualitative and quantitative information about the chemical reactions that take place in interstellar clouds, because only then can you understand the observations and try to reproduce them with models,” says Professor Harold Linnartz, head of El Astrophysics Laboratory. In these interstellar clouds, the material forms from which new stars and planets emerge. The evidence that methane ice forms in these interstellar clouds supports the idea that the methane we now find in Titan’s atmosphere, for example, was already present before our solar system took shape. However, it is unclear how the methane formed in interstellar space eventually ended up on those planets. “Astrochemists are trying to better understand how and what materials pass from interstellar space to protoplanetary disks and ultimately to planetary systems,” said Qasim. “We don’t know exactly how methane ice entered Titan’s atmosphere. A well-heard scenario is that dust particles clump together into larger objects, such as comets, and that they hit planets in the early years of our solar system, acting as a kind of chemical mail carrier. “What researchers can say It is certain that conditions continually changed during the period when our solar system took shape. “This means that the solid methane that forms in interstellar space is an important starting point for the formation of other, more complex molecules.”
Implications
Research gives us more information about the origin of methane. “Now that we know under what conditions methane is formed, we can get a better idea of the relationship between the methane that forms in interstellar clouds and the methane that we see on planets, moons, comets, etc.,” says Qasim. “Since we know how methane is formed, we can also predict where the highest densities of this substance occur in a protoplanetary disk and where the planet methane gas is most likely to be in the atmosphere.”
Imitating conditions in space is not easy. And mimicking methane icing is also tricky. Much more difficult than mimicking the formation of ammonia water and ice, something the Leiden researchers previously did. That has everything to do with the carbon atoms it takes to make methane. In fact, carbon is quite sticky. “Therefore, it is a challenge to make a controlled package of pure carbon atoms. And at the same time, of course, you don’t want your setup to be completely carbon-covered after an experiment. “Despite the challenges that come with the job, the latest experiments in particular still have more flavor.” Now that we know that the Methane can be formed by a reaction between carbon and hydrogen atoms, our next question is: can we make even more complex molecules containing carbon atoms? “Experiments at the Leiden Observatory now allow the formation of larger complex organic molecules, from a way that has not been previously investigated. Qasim: “This is the future of this investigation. So we are going to do that now.”
Keep asking yourself ✨
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