Scientists Can Detect Signs Of Life Remotely

Scientists can detect signs of life remotely and it could be a milestone on the path to detecting life on other planets.

Scientists under the leadership of the University of Bern and of the National Centre of Competence in Research can now detect a key molecular property of all living organisms from a helicopter flying several kilometres above ground. The measurement technology could also open up opportunities for remote sensing of the Earth.

Left hands and right hands are almost perfect mirror images of each other. But whatever way they are twisted and turned, they cannot be superimposed onto each other. This is why the left glove simply will not fit the right hand as well as it fits the left. In science, this property is referred to as chirality.

Just like hands are chiral, molecules can be chiral, too. In fact, most molecules in the cells of living organisms, such as DNA, are chiral. Unlike hands, however, that usually come in pairs of left and right, the molecules of life almost exclusively occur in either their “left-handed” or their “right-handed” version. They are homochiral, as researchers say. Why that is, is still not clear. But this molecular homochirality is a characteristic property of life, a so-called biosignature.

As part of the MERMOZ project, an international team of scientists led by the University of Bern and the National Centre of Competence in Research NCCR PlanetS, has now succeeded in detecting this signature from a distance of two kilometres and at a velocity of 70 kph.

Jonas Kuhn, MERMOZ project manager of the University of Bern, said, “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.”

An instrument that recognizes living matter

“When light is reflected by biological matter, a part of the light’s electromagnetic waves will travel in either clockwise or counter clockwise spirals. This phenomenon is called circular polarization and is caused by the biological matter’s homochirality. Similar spirals of light are not produced by abiotic non-living nature,” said Lucas Patty, who is a MERMOZ postdoctoral researcher at the University of Bern and member of the NCCR PlanetS,

Measuring this circular polarization, however, is challenging. The signal is faint and typically makes up less than one percent of the light that is reflected. To measure it, the team developed a dedicated device called a spectropolarimeter. It consists of a camera equipped with special lenses and receivers capable of separating the circular polarization from the rest of the light.

Yet even with this elaborate device, the new results would have been impossible until recently.

“Just four years ago, we could detect the signal only from a very close distance, around 20 cm, and needed to observe the same spot for several minutes to do so,” said Patty.

But the upgrades to the instrument he and his colleagues made, allow a much faster and stable detection, and the strength of the signature in circular polarisation persists even with distance. This rendered the instrument fit for the first ever aerial circular polarization measurements.

Useful measurements on earth and in space

Using this upgraded instrument, dubbed FlyPol, scientists demonstrated that within mere seconds of measurements they could differentiate between grass fields, forests and urban areas from a fast-moving helicopter. The measurements readily show living matter exhibiting the characteristic polarization signals, while roads, for example, do not show any significant circular polarization signals. With the current setup, they are even capable of detecting signals coming from algae in lakes.

After their successful tests, the scientists now look to go even further.

“The next step we hope to take, is to perform similar detections from the International Space Station (ISS), looking down at the Earth. That will allow us to assess the detectability of planetary-scale biosignatures. This step will be decisive to enable the search for life in and beyond our Solar System using polarization,” said Brice-Olivier Demory, professor of astrophysics at the University of Bern.

The sensitive observation of these circular polarization signals is not only important for future life detection missions.

“Because the signal directly relates to the molecular composition of life and thus its functioning, it can also offer valuable complementary information in Earth remote sensing,” added Patty.

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