For The First Time, A Critical Property of Life Has Been Detected at Extreme Altitude
Make a fist in front of your face. They will be mirrored duplicates of each other for the majority of people: you may hold them palm-to-palm and they will match, but you cannot superimpose them.
Molecules, too, display this chirality, or handedness. They come in two mirrored, non-superimposable configurations. And it is an enthralling quirk of nature that practically all biomolecules can only function in one of their two states.
Natural amino acids are usually always left-handed, or sinistral. Natural sugars, on the other hand, such as those found in RNA and DNA, are usually always right-handed, or dextral. When one of these molecules is replaced with another, the entire system collapses.
This peculiarity is referred to as homochirality. Although we do not understand why this occurs, it is believed to be a critical feature of life. And now, scientists have identified molecular homochirality from a helicopter traveling at a speed of 70 kilometers per hour (43.5 miles per hour) at a height of 2 kilometers (1.2 miles).
You may wonder why they would do such a thing. To determine if molecular homochirality can be detected on other planets in the search for extraterrestrial life. Even here on Earth, it would be beneficial to be able to measure this signal from altitude, as it can provide information about the health of plants.
“When light is reflected by biological matter, a part of the light’s electromagnetic waves will travel in either clockwise or counterclockwise spirals,” noted physicist Lucas Patty of Switzerland’s University of Bern.
“This phenomenon is referred to as circular polarization and is generated by the homochirality of biological matter. Abiotic, non-living nature does not produce similar spirals of light.”
However, as one might imagine, this signal is exceedingly feeble. Vegetation’s circular polarization accounts for less than 1% of the light reflected.
A spectropolarimeter is one sort of equipment that can detect the signal of polarized light. It uses special sensors to isolate the polarized fraction. Patty and his team have been developing an extremely sensitive spectropolarimeter for measuring the circular polarization of plants for several years. Called TreePol, it was capable of detecting circular polarization from a distance of many kilometers.
They have now updated TreePol for flight, adding temperature control to the optics and upgrading the spectrographs. FlyPol is the name of this innovative design.
When Patty and his team flew over Switzerland’s Val-de-Travers and Le Locle using FlyPol, the benefits of these changes became instantly obvious.
“The significant advance is that these measurements have been performed in a platform that was moving, vibrating and that we still detected these biosignatures in a matter of seconds,” said astronomer Jonas Kühn of the University of Bern and MERMOZ project leader (Monitoring planEtary suRfaces with Modern pOlarimetric characteriZation).
It was not only that FlyPol was capable of isolating and discriminating the circular polarization signal from abiotic surfaces such as asphalt highways. The researchers might use it to distinguish between different types of flora, including grass, forests, and even algae in lakes, all from the perspective of a fast-moving helicopter.
This could pave the way for a whole new method of monitoring the health of various vegetative ecosystems, including possibly coral reefs, the researchers added. However, they are not yet finished refining it. They intend to accelerate it to a speed of around 27,580 kilometers per hour and a height of 400 kilometers – low Earth orbit.
“The next step we hope to take is to perform similar detections from the International Space Station (ISS), looking down at the Earth,” astronomer Brice-Olivier Demory of the University of Bern and MERMOZ explained.
While the resolution will be less fine at that height – perhaps 6 to 7 kilometers – it will allow the researchers to fine-tune their spectropolarimeter and determine how well it performs at more extreme scales.
“This will enable us to analyze the detectability of biosignatures at the planetary scale. This approach will be critical in enabling the use of polarization to hunt for life within and beyond our Solar System “As Demory stated.
The research is scheduled for publication in the journal Astronomy & Astrophysics.