Left hands and right hands are almost perfect mirror images of each other. But however they are twisted and rotated, they cannot be laid on top of each other. Therefore, the left glove on the right hand just doesn’t fit as well as the left. In science, this property is called chirality.

Just as hands are chiral, so can molecules be chiral. In fact, most of the molecules in the cells of living organisms, such as DNA, are chiral. In contrast to hands, which normally appear in pairs from left and right, the molecules of life appear almost exclusively in their “left-handed” or “right-handed” version. They are homochiral, as researchers say. Why this is so is not yet clear. But this molecular homochirality is a characteristic of life, a so-called biosignature.

As part of the MERMOZ project (see info box), an international team led by the University of Bern and the National Research Center NCCR PlanetS has now succeeded in creating this signature from a distance of 2 kilometers and a speed of 70 km / h. Jonas Kühn, MERMOZ project leader at the University of Bern and co-author of the study that has just been published in the journal Astronomy and Astrophysics, says: “The main progress is that these measurements were carried out in a moving platform. vibrates and we still discovered these biosignatures within seconds. “

An instrument that recognizes living matter

“When light is reflected by biological matter, some of the light’s electromagnetic waves travel either clockwise or counterclockwise. This phenomenon is called circular polarization and is caused by the homochirality of biological matter. Similar light spirals are not generated by abiotic, inanimate nature, ”says the first author of the study Lucas Patty, MERMOZ postdoctoral fellow at the University of Bern and member of the NCCR PlanetS.

However, measuring this circular polarization is challenging. The signal is quite weak and usually makes up less than one percent of the reflected light. To measure it, the team developed a special device called a spectropolarimeter. It consists of a camera equipped with special lenses and receivers that can separate the circular polarization from the rest of the light.

But even with this complex device, the new results would have been impossible until recently. “4 years ago we could only see the signal from a very short distance, around 20 cm, and we had to
watch the same spot for several minutes, ”recalls Lucas Patty. But the upgrades of the instrument developed by him and his colleagues allow a much faster and more stable detection, and the strength of the signature with circular polarization is retained even with distance. This made the instrument fit for the first circular polarization measurements from the air.

Useful measurements on earth and in space

Using this improved instrument called FlyPol, they demonstrated that they could distinguish between grass fields, forests and urban areas within seconds of taking measurements from a fast-moving helicopter. The measurements readily show that living matter has the characteristic polarization signals, while roads, for example, have no significant circular polarization signals. With the current setup, they are even able to recognize signals from algae in lakes.

After the successful tests, the scientists now want to go further. “The next step we hope is to do similar detections from the International Space Station (ISS) looking down on Earth. This will enable us to assess the detectability of biosignatures on a planetary scale. This step will be crucial in order to use polarization to search for life in and outside of our solar system, ”says MERMOZ research director and co-author Brice-Olivier Demory, professor of astrophysics at the University of Bern and member of the NCCR PlanetS.

Sensitive observation of these circular polarization signals is not only important for future life detection missions. Lucas Patty explains: “Since the signal is directly related to the molecular composition of life and thus its functioning, it can also provide valuable supplementary information in terrestrial remote sensing.” It can provide information on deforestation or plant diseases, for example. When monitoring poisonous algal blooms, coral reefs and their effects through acidification, circular polarization could even be implemented.


Publication information:

CH Lucas Patty et. Al., Biosignatures of the Earth I. Airborne spectropolarimetric detection of photosynthetic life, Astronomy & Astrophysics
https: //doi.Organization/10.1051 /0004-6361 /202140845

SAINT-EX – Search and characterization of exoplanets

The SAINT-EX research group (funded by the SNSF professorship of Prof. Brice-Olivier Demory) focuses on:

    -Detection of moderate earth-sized exoplanets (SAINT-EX observatory),

    – Remote sensing of life in planetary atmospheres / surfaces (MERMOZ),

    -Instruments for non-invasive in vivo cancer diagnosis and staging (BrainPol).

The MERMOZ (Monitoring planEtary surfaces with Modern pOlarimetric CharacteriZation) project aims to investigate whether we can identify and characterize life on earth from space by building a benchmark library of surface feature signatures using remote full Stokes spectropolarimetry . In this context, our planet is viewed as a proxy for other bodies in the solar system and exoplanets.

MERMOZ is a partnership project between the Universities of Bern, Leiden and Delft (NL).

The feasibility study of the project is funded by the Center for Space and Habitability (CSH) and the NCCR PlanetS.

Further information on the SAINT-EX / MERMOZ research group: https: //www.Saintex.unibe.CH /

NCCR PlanetS: Planetary research made in Switzerland

In 2014, the Swiss National Science Foundation awarded the University of Bern the National Center for Competence in Research (NFS) PlanetS, which it runs jointly with the University of Geneva.

Since taking part in the first moon landing in 1969, the University of Bern has participated in space missions by major space organizations such as ESA, NASA, ROSCOSMOS and JAXA. It currently heads the European Space Agency’s (ESA) CHEOPS mission together with the University of Geneva. In addition, Bern researchers are among the best in the world when it comes to models and simulations of the formation and development of planets.

With the discovery of the first exoplanet, the University of Geneva positioned itself as one of the leading institutions in this field. This led, for example, to the construction and installation of the HARPS spectrograph on the 3.6 m telescope of ESO on La Silla under the direction of Geneva in 2003. This was followed by the ESPRESSO instrument on ESO’s VLT telescope in Paranal. The “Science Operation Center” of the CHEOPS mission is also located in Geneva.

The ETH Zurich and the University of Zurich are also partner institutions in the NCCR PlanetS. Scientists from the fields of astrophysics, data processing and geosciences lead projects and make important contributions to research at the NCCR PlanetS. In addition, ETH is a world leader in instrumentation for various observatories and space missions.

The NCCR PlanetS is divided into the following research areas:

    -Early stages of planet formation

    -Architecture of planetary systems, their formation and development

    – Atmospheres, surfaces and the interiors of planets

    – Determination of the habitability of planets.

More information: http: // nccr-planets.CH /

Bernese space research: with the world’s elite since the first moon landing

When the second man, “Buzz” Aldrin, got off the lunar module on July 21, 1969, his first assignment was to set up the Bern Solar Wind Composition Experiment (SWC), also known as the “solar wind sail” from it into the bottom of the moon plant, even before the American flag. This from Prof. Dr. The experiment planned and analyzed by Johannes Geiss and his team from the Physics Institute of the University of Bern was the first major highlight in the history of space research in Bern.

Space research in Bern has belonged to the world’s elite ever since. The University of Bern participates in space missions of the major space organizations such as ESA, NASA, ROSCOSMOS and JAXA. It is currently leading the CHEOPS mission of the European Space Agency (ESA) together with the University of Geneva. In addition, Bern researchers are among the best in the world when it comes to models and simulations of the formation and development of planets.

The successful work of the Department of Space Research and Planetology (WP) of the Physics Institute of the University of Bern was consolidated by the establishment of a university competence center, the Center for Space and Habitability (CSH). The Swiss National Science Foundation has also awarded the University of Bern the National Research Center (NCCR) PlanetS, which it manages together with the University of Geneva.


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