Press releases – January 2019

FRANKFURT. Should regulations for environmental protection be valid beyond our solar system? Currently, extra-terrestrial forms of life are only deemed worth protecting if they can be scientifically investigated. But what about the numerous, presumably lifeless planets whose oxygen atmospheres open up the possibility of their settlement by terrestrial life forms? Theoretical physicist Claudius Gros from Goethe University has taken a closer look at this issue. 

On earth, environmental protection has the primary goal of ensuring the availability of clean water and clean air for human beings in the future. Human interests usually take also precedent when it comes to protecting more developed animals and plants. Lower life forms such as bacteria, on the other hand, are considered worthy of protection only in exceptional cases. 

Claudius Gros, professor for theoretical physics at Goethe University, has now investigated the degree to which the norms for the protection of planets can be derived analogously from issues that arise in environmental protection on Earth. The international COSPAR agreements on space research stipulate that space missions must ensure that any existing life – such as possibly on the Jupiter moon Europa – or traces of previous life forms – perhaps on Mars – are not polluted, so that they remain intact for scientific purposes. The protection of extra-terrestrial life as valuable in and of itself is not stipulated. 

The COSPAR Guidelines apply to our solar system. But to which extent should they be applied to planetary systems beyond our solar system (exoplanets)? This will become a relevant issue with the advent of launch pads for miniature interstellar space probes, such as of the type in development by the “Breakthrough Starshot" initiative. Gros argues that the protection of exoplanets for the use of humankind could not be justified. Apart from fly-bys, we could carry out scientific studies only with space probes able to slow down in an alien solar system. Using the best technology available today, this would require magnetic sails and missions lasting thousands of years, at the least. 

According to Gros, the protection of exoplanets would also be irrelevant if these planets were lifeless, even if they were otherwise habitable. This probably includes planet systems such as the Trappist-1 system, whose central star is an M-dwarf star. Planets orbiting in the habitable zone of an M-dwarf star have a dense oxygen atmosphere that was formed through physical processes before cooling. Whether life can develop on such planets is questionable. Free oxygen acts corrosively on prebiotic reaction cycles, which are considered prerequisites for the origin of life. “Whether there is another way for life to form on these oxygen planets is an open question at this time," says Gros. “If not, we would find ourselves living in a universe in which most of the habitable planets are lifeless, and thus suitable for settlement by terrestrial life forms," he adds.

Publications: Claudius Gros: Why planetary and exoplanetary protection differ: The case of long duration Genesis missions to habitable but sterile M-dwarf oxygen planets, Acta Astronautica 2019, in press. https://arxiv.org/abs/1901.02286 

Claudius Gros: Developing Ecospheres on Transiently Habitable Planets: The Genesis Project, Astrophysics and Space Science 361, 324 (2016) http://link.springer.com/article/10.1007/s10509-016-2911-0

FRANKFURT. Archaeologists from Goethe University will be returning to the Urals for further research work. In collaboration with researchers from Johannes Gutenberg University Mainz and Russian colleagues, they want to find out what could have led to major transformations in the way of life there in the second millennium BC. The project has been awarded funds of € 600,000 by the German Research Foundation, initially up until the end of 2020. The research work follows on from an earlier project undertaken between 2009 and 2014.

The aim of the project is to reconstruct demographic processes and settlement structures in the late Bronze Age up to the transition to the Iron Age – what is known as the post-Sintashta-Petrovka period. Artefacts discovered so far have shown that the southern Trans-Ural region at the dividing line between Europe and Asia on the northern edge of the Eurasian Steppe constitutes a unique cultural landscape. Superb Bronze and Iron Age monuments, such as burial mounds (“kurgans") and settlements, show that this was a centre of economic development and sociocultural processes that already began in the third millennium BC. After the decline of fortified settlements, the housing structure changed and “open" settlements with terraced houses without fortifications emerged. Russian research dates these settlements to the middle of the second millennium BC, i.e. the Late Bronze Age.

During the research phase that lasted from 2008 to 2014, Professor Rüdiger Krause devoted himself above all to the fortified settlements of the Sintashta-Petrovka period (around 2000 BC). Characteristic for this culture were early chariots, intensive copper mining and substantial bronze production. Attention has now shifted to various other archaeological sites of the Bronze and Iron Ages in the microregion at the confluence of the Yandyrka and Akmulla rivers and the upper end of the Karagaily-Ayat valley. How have settlement structures evolved? How was the landscape used as the economic foundation for livestock farming? And how have funeral customs changed? The intention is to study the demographic processes underlying all this in the course of the project, using not only palaeogenetic techniques but also archaeological excavations, geophysical surveys, interpretation of the material culture and archaeobotany. 

Who were the people responsible for the shift at that time from a settled form of existence to a nomadic way of life? Where did they originate from and how did they come to arrive in the Urals? Archaeology and palaeogenetics will work hand in hand in the search for answers to these questions. One of the aims of this collaboration is to analyse population genetics using state-of-the-art genome analysis methods. 

The team led by Professor Joachim Burger at the University of Mainz is specialised in the analysis of genomes from archaeological skeletons. In the framework of this project, the palaeogenetics experts from Mainz will examine the question of to what extent genetic influences from Europe or the central Asian steppe coincide with the cultural transformation to be observed in the Trans-Ural region. Was it foreigners who introduced the change? Or did regional cultural developments take place here? How have demography and population structure changed over the millennia? To find answers to these questions, the researchers from Mainz will use high-resolution sequencing to study the genomes from the project's archaeological sites and analyse them with statistical methods they have developed themselves, in order to unearth as much detailed information as possible about the people of the Bronze and Iron Ages. 

A report on the first phase of the research project can be read (in German) in Forschung Frankfurt, 1.2012, pp. 32-36: “Innovationwen vor 4000 Jahren in der Eurasischen Steppe. Streitwagenfahrer und Metallurgen in befestigten Siedlungen“ by R. Krause and J. Fornasier. 

Further information: Professor Rüdiger Krause, Institute of Archaeological Sciences, Prehistory and Early History, Westend Campus, Norbert-Wollheim-Platz 1, Tel.: +49(0)69-798-32120; https://www.uni-frankfurt.de/61564916/LOEWE-Schwerpunkt 

Professor Joachim Burger, Palaeogenetics Group, Institute of Organismic and Molecular Evolution (iomE), Johannes Gutenberg University Mainz, Anselm-Franz-von-Bentzel-Weg 7, 55128 Mainz, Tel.: +49(0)6131-39-20981; http://palaeogenetics-mainz.de 

Image material can be downloaded from: http://www.uni-frankfurt.de/75784479 

Captions: 01 Trans-Ural region. Konopljanka-2 Bronze Age terraced house settlement with a filled-in well shaft in the foreground. 2018 excavation. © Ural Project, Goethe University

02 Trans-Ural region, Neplujevka. Burial of an adult in a large kurgan. Late Bronze Age, 2017 excavation. © Ural Project, Goethe University 

03 Trans-Ural region, Neplujevka. Burial of a young person in a large kurgan. Late Bronze Age, 2016 excavation. © Ural Project, Goethe University 

04 University of Mainz, documentation of bone samples in the cleanroom laboratory in preparation of palaeogenetic tests. © Joachim Burger, JGU Mainz 

05 University of Mainz, preparation of bone samples in the cleanroom laboratory for genome analysis. © Joachim Burger, JGU Mainz

FRANKFURT. Insulators that are conducting at their edges hold promise for interesting technological applications. However, until now their characteristics have not been fully understood. Physicists at Goethe University have now modelled what are known as topological insulators with the help of ultracold quantum gases. In the current issue of Physical Review Letters, they demonstrate how the edge states could be experimentally detected. 

Imagine a disc made of an insulator with a conducting edge along which a current always flows in the same direction. “This makes it impossible for a quantum particle to be impeded, because the state of flowing in the other direction simply doesn't exist," explains Bernhard Irsigler, the first author of the study. In other words: in the edge state, the current flows without resistance. This could be used, for example, to increase the stability and energy efficiency of mobile devices. Research is also being done on how to use this to construct lasers that are more efficient. 

In recent years, topological insulators have also been produced in ultracold quantum gases in order to better understand their behaviour. These gases result when a normal gas is cooled down to temperatures between a millionth and billionth of a degree above absolute zero. This makes ultracold quantum gases the coldest places in the universe. If an ultracold quantum gas is also produced in an optical lattice made of laser light, the gas atoms arrange themselves as regularly as in the crystal lattice of a solid. However, unlike a solid, many parameters can be varied, allowing artificial quantum states to be studied. 

“We like to call it a quantum simulator because this kind of system reveals many things that take place in solids. Using ultracold quantum gases in optical lattices, we can understand the basic physics of topological insulators," explains co-author Jun-Hui Zheng. 

A significant difference between a solid and a quantum gas, however, is that the cloud-shaped gases do not have defined edges. So how does a topological insulator in an ultracold gas decide where its edge states are? The researchers in Professor Walter Hofstetter's research group at the Institute for Theoretical Physics at Goethe University answer this question in their study. They modelled an artificial barrier between a topological isolator and a normal isolator. This represents the edge of the topological insulator along which the conducting edge state forms. 

“We demonstrate that the edge state is characterized through quantum correlations that could be measured in an experiment using a quantum gas microscope. Harvard University, MIT and the Max-Planck-Institute for Quantum Optics in Munich all carry out these kinds of measurements," says Hofstetter. A quantum gas microscope is an instrument with which individual atoms can be detected in experiments. “For our work, it is critical that we explicitly take into account the interaction between the particles of the quantum gas. That makes the investigation more realistic, but also much more complicated. The complex calculations could not be carried out without a supercomputer. The close collaboration with leading European scientists within the context of the DFG Research Unit 'Artificial Gauge Fields and Interacting Topological Phases in Ultracold Atoms' is also of particular importance for us," Hofstetter adds. 

Publication: Bernhard Irsigler, Jun-Hui Zheng, and Walter Hofstetter: Interacting Hofstadter interface, Physical Review Letters, https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.122.010406 

A picture can be downloaded at: http://www.uni-frankfurt.de/75773481

Caption: Artificial edge in an optical lattice (blue), filled with an ultracold quantum gas that consists of 'spin-up' particles (red) and 'spin-down' particles (green). Along the edge – and only there - 'spin-up' particles can only flow to the left, and 'spin-down' particles can only flow to the right. Credit: Bernhard Irsigler 

Further Information: Bernhard Irsigler, Institute for Theoretical Physics, Riedberg Campus, Tel.: +49 69-798 47883, irsigler@th.physik.uni-frankfurt.de .

FRANKFURT. Diamonds are messengers from Earth's interior. A portion of the rare gem, which is very small but important for researchers, contains inclusions from the earth's lower mantle. One of the most common minerals brought to the Earth's surface in this way has now been named “breyite" by the Commission of the “International Mineralogical Association" in honour of the mineralogist Professor Gerhard Brey from Goethe University.

The interior of the Earth is largely inaccessible for sample recovery. Intensive drilling efforts can reach a maximum depth of 12 kilometres, which represents a mere scratching on the surface. Volcanoes, on the other hand, can transport samples from significantly deeper zones to the Earth's surface. The samples that come from the greatest depths are inclusions of minerals and rock fragments in valuable diamonds. These inclusions were one of the fields of research of Gerhard Brey, meanwhile retired Professor for Petrology and Geochemistry at the Institute for Geosciences at Goethe University. 

According to prevalent theories, Earth's lower mantle (at a depth of 660 – 2900 kilometres) consists almost exclusively of the three minerals silicate perovskite, ferropericlase, and a mineral rich in calcium and silicon with a perovskite structure. When diamonds form at this depth, it can happen that they trap this mineral. During transport to the earth's surface, the calcium-silicon perovskite converts to a new crystal structure that is stable at lower pressure. This mineral is only known as inclusion in diamonds. It now bears the name breyite. 

“Having a mineral named after you is a very special honour and pays tribute to the life work of a scientist in a special and lasting way," states Brey's colleague, the geoscientist Professor Frank Brenker. “Especially when we're talking about such an important Earth mineral. 

Gerhard Brey's name is now forever carved in stone, so to speak." Gerhard Brey, who retired in 2014, is considered a pioneer in experimental petrology under high-pressure conditions. He achieved world recognition through the development and calibration of geothermobarometers for rocks in the earth's mantle. These thermobarometers are not only crucial aids in researching the Earth's interior, they are also very popular in the search for new diamond deposits. While it used to be necessary to process tons of rocks to determine whether the deposit in question really contained diamonds, now only a few grains of mineral are necessary. 

In addition to thermobarometric calculations, Brey is interested in the solubility of fluids and gases, including their influence on the formation of magmas. Along with other colleagues, he was one of the first researchers to recognize the scientific value of inclusions in diamonds with origin depths of hundreds of kilometres. Brey has received a numerous distinctions, including an honorary doctorate from the Russian Academy of Sciences and the Abraham-Gottlob-Werner silver medal, which he was awarded by the German Mineralogical Society for his life's work. 

A picture may be downloaded at: www.uni-frankfurt.de/75659882 

Caption: Breyite inclusion in a Brazilian diamond with “super-deep“ origins. 

Credit: Brenker, Goethe University Portraits of Gerhard Brey: private 

Further Information: Professor Frank Brenker, Institute for Geosciences, Mineralogy, Riedberg Campus, Tel.: (069)-798 40134, f.brenker@em.uni-frankfurt.de.