Mysteries of UNIL: In Géopolis we track down the origin of life

If one day we manage to unravel the mysteries of the origins of everything that surrounds us – from the formation of rocks to the appearance of life on Earth – there is a good chance that it will come to us from the maze of the Geopolis building, the University of Lausanne.

For almost twelve years, researchers have been working discreetly around the devices of the Center for Advanced Surface Analysis (CASA), a consortium of laboratories from UNIL and EPFL. And in particular the SwissSIMS probe. An incredible tangle of vacuum tubes, connected by an army of cables and detectors. A multi-million franc device, shared by the EPFZ and the universities of Lausanne, Geneva and Bern. “Machines of this kind, capable of this much precision, there are perhaps around twenty of them in the world. And again,” breathes Johanna Marin-Carbonne.

Valuable progress

In recent years, SwissSIMS has already made significant progress. Not necessarily by answering questions from Mr. or M.^me Everyone, but real leaps for researchers interested in the origin of matter. In 2021, a trio of specialists managed to explain the high temperatures – from 50 to 70 degrees – which are hidden behind the formation of the first marine rocks. They would be the result of currents or sources, and not necessarily proof that the primitive sea was a furnace.

“We managed to measure the age of meteorites,” says Johanna Marin-Carbonne. We know more about how the Alps were formed: about the pressures exerted at depth on the rocks which gave rise to the Monte Rosa massif, for example. This is the great advantage of SwissSIMS, we are lucky to be able to analyze exceptional samples.”

Expensive places

On the day of our visit, the professor does not take her eyes off the armada of screens which allow us to monitor the operation of the instruments in real time, well sheltered behind the windows of a pressurized room. The material samples, arranged on tiny washers, are placed in a small chamber powered by 10,000 volts. In one click, let’s go. A beam of ions is projected onto the sample, leaving a hole that measures just a tenth of a hair. The material is projected into the mass spectrometer, accelerated, passed through a magnetic field and finally analyzed in a series of detectors.

That day, it was a doctoral student’s samples that went through the machine. We must act quickly. The researcher submits his thesis in a few weeks and this is his last slot: the schedule is full until the end of August. We start with a reference sample, aimed at checking the stability of the enormous device.

The oxygen isotope data taken from the detectors are clearly displayed on a table. The raw reports, number of blows per second, the errors… Columns of figures which will perhaps allow us to go back to the fluids which formed this primitive granite. But nothing works. The deviations are too significant compared to the reference values. A first then a second “crepe”.

Small problem

In the jargon, it is the inevitable first failure, as in cooking. Not too serious, as long as it’s not a portion of the millions of years old samples that pass through the optics of the mass spectrometer. “But there is still a problem,” sighs Anne-Sophie Bouvier, the laboratory manager. Something is wrong.

It must be said that the measurements are so precise – the main current is a billionth of an ampere… – that the slightest breath of air in the analysis room can change the situation. The settings continue. The analyzes start anyway.

In search of origins

The researchers who revolve around the tool are currently looking at micro samples from Ryugu, some dust from the asteroid, one of the oldest in the solar system, on which the Japanese probe Hayabusa 2 managed to land in 2019. An extremely rare feat, which brought never-altered matter back to Earth, like a meteorite which passed through the atmosphere and remained for centuries in a desert. An incredible opportunity. The people of Lausanne hope to determine the origin of the sulfur contained in Ryugu, between the primordial one of the solar system, or the late one of the alteration fluids in space.

But what keeps Johanna Marin-Carbonne very busy are stromatolites. Kinds of small rocks, made up of thin layers left by bacteria. They are found in certain lakes. But the oldest date back more than 3.5 billion years ago. At the beginning of the Precambrian, these primitive fossils bear the traces left by the oldest forms of life known on Earth.

She opens a small, conditioned and locked cupboard. “Here there is a stromatolite that is 2.5 billion years old and comes from South Africa. It was dated by analyzing the isotopes of uranium, lead in zircons and volcanic ash associated with it. When trapped in zircon, a very resistant mineral, uranium decreases over time. Which provides a sort of stopwatch in fact. Knowing that it is not the oldest, there is one here of 3.5 billion years. He comes from Australia and we still haven’t dared to touch him.”

“Afterwards, it remains to be seen whether bacteria are at the origin of these rocks or not, and which ones,” notes Johanna Marin-Carbonne. What we are going to do is try to find their signature through the sulphide that certain bacteria consume. On the main lines.”

From the lab to mountain lakes

To better identify the different families of bacteria, several projects are underway, with microbiologists, who are trying to find out what sulfide these bacteria produce and under what conditions. When they are alone, and when they are together. The work takes place in the laboratory, in a controlled environment, but also in the mountains, in the lakes of St. Moritz and Zermatt. It then remains to see what worked and compare the results.

In each case, potentially great progress. “We hope in a few years to better understand the sulfur cycle in the past,” concludes the researcher. These interdisciplinary projects can have big implications for our understanding of how the Earth formed.”

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