Monday , August 15 2022

Simulate cosmic nature laboratory, one drop helium at a time


** Cosmic nature laboratory simulation, one drop helium at a time

Schematic representation of the new method: Two reactors R1 and R2 are added to a helium drop. The energy released in the resulting reaction reduces the size of the droplet. The reduction in size can be measured, and allows researchers to extract energy from the reaction. Credit: Krasnokutskiy / MPIA

Two astronomers from the Max Planck Institute of Astronomy and the University of Jena have found a delicate new method to measure the energy of simple chemical reactions, under conditions similar to those seen by atoms and molecules in the early solar system. Their method promises accurate measurements of the energy of reactions that can be used to understand chemical reactions under space conditions – including those reactions that were responsible for creating organic chemicals as the raw material for life development.

For life to form, nature needed enough raw materials in the form of complex organic molecules. Some of those molecules are likely to have been formed long before, in space, during the birth of the solar system. Systematic studies of the necessary chemical reactions, occurring on rocky and invasive surfaces of dust particles, were hampered by a lack of data. What elementary reactions include what individual reactors are possible? What temperature is needed for a reaction to occur? Which molecules are produced in those reactions? Now, Thomas Henning, director of the Max Planck Institute of Astronomy (MPIA), and Sergiy Krasnokutskiy of the Astronomy Laboratory Group of the MPIA at Jena University, has developed an elegant approach to the study of superficial reactions of this type – using drops. fluid helium minutes.

In the early solar system, long before the formation of the Earth, there was a complex chemical reaction, creating substantial amounts of organic molecules. The cosmic laboratory for this work of chemical synthesis was provided by particles of dust – mainly clusters of silicon and carbon, covered with ice mantle, with complex and fragile tenders and implications, and on this basis with one essential property: A relatively large surface that chemical reactions may occur. In the millions of years that followed, a lot of that dust grain would cluster with each other for even larger structures, until solid planets came to the t Ultimately obvious, surrounded by the young Sun.

Create the raw ingredients for life

Although all organic compounds synthesized on the grain surfaces would be destroyed by the inevitable heat during the formation of the planet, some of the molecules remained, being concentrated in. , or tied to the surface of small rock or lumps, as well as in the icy bodies of the comets. On one account of life history, once the surface of the Earth had cooled enough for liquid water to form, the grains and these rocks, hitting the Earth's surface in the form of meteorites, some of which landed in warm, small ponds, provided the chemical basis for life was formed on our home planet.

To understand the early natural chemical experiments in our universe, we need to know the properties of the different reactions. For example, do some reactions require specific activation energy? What is the ultimate reaction product? Those parameters determine what reactions can occur under what conditions in the early solar system, and are key for any realistic reconstruction of the solar system's early chemistry.

Rare data about low temperature surface reactions

Again, accurate data on these reactions is remarkably rare. Instead, a significant part of chemical research has been devoted to the study of such reactions in the gaseous period, with the atoms and molecules floating freely, in conflict, and t forming compounds. But the vital chemical reactions in the space needed to build larger organic molecules occur under very different conditions – on dust grain surfaces. This changes even the basic physics of the situation: When a new molecule is formed, the energy of the formation of the chemical bond is stored in the newly created molecule. If this energy is not transferred to the environment, the new molecule is quickly destroyed. This prevents the formation of many species in the gas phase. On a surface, or in a medium, where energy can be easily absorbed by the additional issue present, the conditions are for certain types of reactions that build complex molecules, step t by step, much more favorable.

Henning and Krasnokutskiy developed an elegant method for measuring energy energy of this kind. Their forgery of cosmic laboratories are small helium droplets, few nanometers in size, drifting in high vacuum. The reactors – that is, the atoms or molecules intended to participate in the reaction – were brought into the vacuum chamber as gases, but in such minutes helium drops are likely raise either a single molecule of each species required or none, but no more. The helium drops act as a medium that, similar to the surface of dust grains, can absorb the energy of a reaction, allowing reactions to occur under conditions similar to those in the early solar system. This key feature reproduces the relevant surface chemistry (although other properties, such as catalytic properties of a specific dust surface, have not been modeled).

Nanodrops as measuring devices

In addition, both astronomers used the helium nanodrops as energy measuring devices (calorimeters). As the reaction energy is released to the drop, some of the Helium atoms evaporate in a predictable manner. The remaining drop is now less than the tip – a difference in size that can be measured using two alternative methods: an electron beam (a larger fall is easier to hit than a smaller one) t !) Or a detailed measurement of the pressure in the vacuum chamber has been created by Helium droplets hitting the wall, where larger droplets produce more pressure. By calibrating their method using carefully studied reactions in advance, and their properties known, both astronomers were able to significantly increase the accuracy of the method. Overall, the new approach provides an elegant new way of investigating the formation of complex organic molecules in space. This should enable researchers to be more specific about the raw materials that nature must work with as the life ends on Earth. But there is more:

The first measure that uses the new technique confirms a trend that had already been seen in other recent experiments: On surfaces, at low temperatures, carbon atoms are surprisingly reactive t . The researchers found an incredibly high number – nearly a dozen – of reactions involving carbon atoms that are unnecessary, that is, they do not need additional energy input to move on, and so can occur at very low temperatures. . Obviously, atomic gas evaporation at low temperatures is bound to result in the formation of a large range of organic molecules. But that great variety also means that the molecules of each species will be very rare.

This, in turn, suggests that astronomers could be significantly underestimating the amount of organic molecules in the outer space. In terms of estimation of numbers, astronomical observations examine trace signals (spectacle lines) of each molecular species separately. If there are many different types of organic molecules out there, each species can "fly under the radar." Its molecules could be present in quantities too short for astronomers to detect, and in addition, even the legendary signatures of the molecules (certain active groups that are common to different types of molecules could be). general) should be changed slightly, making avoid molecule. But it is possible that all these separate species of molecule could create a significant amount of matter in the outer space – a hidden world of organic chemistry outside it.

Explore further:
Chemistry can change the ingredients when forming the planet

More information:
Thomas K. Henning et al. Experimental characterization of surface temperature low temperature reactions, t Nature Astronomy (2019). DOI: 10.1038 / s41550-019-0729-8

Magazine reference:
Nature Astronomy

Provided by:
Max Planck Society

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