Mars is an inhospitable desert planet. Billions of years ago, things were different. In Jezero Crater, for example, fed by a vast river delta, there was probably a considerable body of water roughly the size of Lake Constance. Conditions conducive to life may have prevailed there.
For more than four years now, the long-dry Jezero Crater has been the workplace of Perseverance. The NASA rover not only performs scientific measurements on site, but has already collected 33 rock, soil, and atmospheric samples, some of which have been safely stowed on board. A future mission is to bring them back to Earth.
Traces of life?
The Jezero crater recently made headlines when researchers discovered small spots resembling a leopard pattern on a rock formation called Cheyava Falls. The structures indicate the presence of two minerals that could be of organic and microbial origin. These minerals are found on Earth in sediments or decaying organic matter. But only when a sample of these structures is analyzed on Earth can it be confirmed or ruled out with a high degree of certainty that they indicate past life on Mars.
“Examining rocks and samples of the Martian atmosphere on Earth will open a new chapter in Mars research and help us understand our neighboring planet much better than we can today,” says Andreas Pack from the Geosciences Center at the University of Göttingen.
Over the past two years, an international team of 21 researchers led by the American and European space agencies NASA and ESA has been exploring how to proceed with Perseverance’s samples from a scientific perspective on Earth. The comprehensive study has now been published in the journal Astrobiology.
Among the authors selected by NASA and ESA from numerous applicants from the US, Canada, and the 22 ESA member states, Christian Schröder from MPS and Pack from the Geosciences Center at the University of Göttingen are the only representatives of German research institutions. NASA recently honored the team with the NASA Group Achievement Award. In another report in the same journal, researchers explore how the Mars samples can be protected from terrestrial contamination. One of the co-authors is Christoph Burkhardt from MPS.
Laboratory tests for final certainty
The samples collected by the Mars rover Perseverance contain valuable information about the formation and further development of Mars and can help to answer the question of whether there has ever been life on our neighboring planet. Measurements taken by Perseverance on Mars suggest this, but do not provide certainty.
“In order to assess with the greatest possible certainty whether life once existed on Mars, we need to bring samples from Mars back to Earth and examine them here,” said Schröder, MPS scientist and co-author of the new study.
The relatively small and few scientific instruments that Perseverance carries on board offer only very limited possibilities. Only on Earth can a wide variety of analytical methods be used, and only here can measurements be carried out with the highest sensitivity and precision.
For their current report, 21 scientists identified which measurements the Mars samples should undergo in order to fully exploit their potential. The researchers hope to gain new insights into the formation of planets, the geophysical and geochemical evolution of Mars, and astrobiology, as well as valuable information for future, possibly even manned, Mars missions.
The report also clarifies practical questions regarding the handling of the samples: which measurements should be carried out as quickly as possible? After all, some properties of the samples could change after the sample tubes are opened. For example, under the influence of humidity and oxygen. And which measurements can prove whether there is life in the samples or rule out a possible biological hazard?
Sample Receiving Facility with 18 instruments
Once on Earth, the Mars samples will first enter into the Sample Receiving Facility. According to the experts’ recommendation, it should be equipped with 18 scientific instruments, including an X-ray tomograph, an electron microscope, and various mass spectrometers.
At the Sample Receiving Facility, scientists would first describe and catalog the samples for further use and assess the potential biological hazard they pose. After that, all time-critical investigations can be carried out. An important finding of the report is that most of the scientifically necessary measurements should be carried out later outside the Sample Receiving Facility in specialized laboratories.
A kind of application process will decide which laboratories worldwide will receive parts of the invaluable material. This procedure ensures that the samples end up in the most experienced and qualified hands. The Göttingen researchers hope to receive both rock and gas samples from Perseverance.
A look at isotopes
The researchers led by Pack from the Geosciences Center at the University of Göttingen want to determine the proportions of oxygen isotopes in the Martian atmosphere that were enclosed in the sample tubes together with the rocks. Isotopes are variants of the same element that differ only in the number of neutrons in their nuclei. The oxygen isotope composition of the Martian atmosphere allows conclusions about the exchange of carbon dioxide between the surface and the atmosphere and provides, for example, insights into the climatic development of our neighboring planet.
At MPS, the focus is on the metal isotopes in the rock samples. Researchers can use them to obtain information about the age of the material, where in the solar system it originated, and how it has evolved. MPS researchers have already examined samples from the asteroid Ryugu in this way.
To do this, the material is first dissolved in acid and then analyzed in highly specialized mass spectrometers. Since this method of analysis destroys the sample material, it is crucial to obtain reliable results even from the smallest amounts of material.
“In Göttingen, we have the expertise and infrastructure to analyze Mars samples at the highest international level,” said Thorsten Kleine, Director at MPS.
The researchers could carry out further investigations at other facilities. Schröder, for example, is focusing on measurements using high-energy gamma radiation generated by particle accelerators. This would allow to trace the interaction of iron minerals in the sample with organic material.
Uncertain future
Whether and when the Mars samples from Perseverance will travel to Earth as part of a joint NASA and ESA mission is currently unclear. The original schedule targeted the early 2030s, but has been changed several times in the meantime. However, the studies now published are also valuable for the projects of other space agencies. For example, the Chinese space agency is currently preparing its own sample return mission to Mars, which is expected to bring the coveted material back to Earth as early as 2030.
Provided by Max Planck Society
