Sandra searches for life in the universe

Even as a child, Sandra Siljeström looked up at the stars and dreamed of space. She was interested in astrobiology and wanted to search for life on other planets. When Sandra was writing her PhD, she had the opportunity to do it for RISE, which had the advanced analytical instrument, ToF-SIMS (time-of-flight secondary ion mass spectrometry), that she wanted to use. Sandra has a PhD in geochemistry and her thesis was on developing new methods to study organic molecules in rocks. She is now an astrobiologist working with NASA and others to find life on Mars.

Life on Mars

Mars was first landed in 1976. Nasa currently has several active probes on Mars, but it has never carried out a Mars sample return project (which will be carried out jointly with ESA). In other words, no one has ever returned samples from Mars to Earth. On 18 February 2021, NASA's Perseverance spacecraft will land on Mars. For the first time, samples from the Martian surface will be brought back to Earth for analysis. The hope is to find signs of life.

"One of the greatest scientific questions is whether we are alone in the universe. If we find active life or traces of fossilised life, it will be a major discovery. If we can also prove that this life on Mars is not related to life on Earth, it means that life could have originated in several other places in the Universe. It's an exciting thought," says Sandra Siljeström.

Landing in the Jezero crater

NASA's 2020 Mars team includes about 400 people from all over the world. Most of them live in North America, but one of the researchers is Sandra Siljeström from Sweden at RISE. Her job is to help choose which samples to collect on Mars and to make sure the right information is collected about those samples. 

"Perseverance landed in the Jezero crater in the Isidis Planitia region of Mars. The crater was created by a meteorite impact and was previously filled with water. We are interested in the river delta that existed there. A delta accumulates material and we believe that this is where we have the best chance of finding traces of fossilised life," says Sandra Siljeström.

In the Jezero crater it should be possible to find rocks that are almost 4 billion years old. But there are clear restrictions on the samples that can be taken. A maximum of 30 samples can be taken, each weighing no more than 0.5 kg. This is because the density of the Martian atmosphere makes it difficult to lift them off the planet. 

The context of the samples is important

Sandra has already analysed rocks from Mars, but these were meteorites and it is not known where on Mars they came from.

"The context is extremely important. Now we will be able to analyse the samples with the knowledge of where they came from and this will give us a much better understanding of Mars," says Sandra Siljeström. 

But it will be some time before the Mars samples reach Earth. It will take up to ten years for the samples, which will start to be collected in 2021, to arrive here.

"I hope that I will have the opportunity to analyse the samples that I have helped to select, but because of the long lead times, you can't be completely sure. The samples are not expected to reach Earth until 2031 at the earliest. Since we only know about life on Earth at the moment, it is important to be agnostic in our search for life on Mars. This means assuming as little as possible to ensure that we do not rule out what we are looking for. And since we don't know what we're looking for, we need to use many different techniques, from chemical to microbiological," says Sandra Siljeström. 

Few space scientists

A lot is happening in space these days. There is a lot of interest, and both public and private actors see opportunities and are taking big steps. Space research used to be extremely expensive, but now that you can reuse both materials and design, it has become a bit more accessible. However, not many people in Sweden are involved in space. Many people do not actually look into space, but use space to study the Earth, for example to monitor climate change.

"At RISE we also work with so-called Earth observations. The RISE Space Data Lab is an initiative of, among others, the Swedish National Space Board and is a national knowledge hub for space data analysis. The aim is to increase the use of space data for the development of society and industry," says Sandra Siljeström.

It's all about chemical problem solving

When Sandra is not working with NASA and Mars, she is working for various industries, including the automotive, energy, chemical and pharmaceutical industries.

"I analyse surfaces using ToF-SIMS, an instrument that can provide chemical information about surfaces at the micrometre level. This can be geological research projects with industry, but it can also be contracts from companies where I analyse surfaces to investigate, for example, why paint is coming off or why different components stick together when they shouldn't. It's all about solving chemical problems," says Sandra Siljeström.

But research into life on Mars is taking up more and more time.

"The interest is growing, which is great," says Sandra Siljeström. "Of course, I encourage others to study and work as astrobiologists. I think the need for good astrobiologists will continue to grow, and I can't think of anything better! Learning more about space is very exciting!"

Images from Mars

Every week, NASA releases pictures taken by the Perseverance rover on Mars. Here are a few examples. See more at NASA.

NASA's Mars Perseverance rover acquired this image using its onboard Right Navigation Camera (Navcam). The camera is located high on the rover's mast and aids in driving.

NASA's Mars Perseverance rover acquired this image using its onboard Left Navigation Camera (Navcam). The camera is located high on the rover's mast and aids in driving.

NASA's Mars Perseverance rover acquired this image using its Left Mastcam-Z camera. Mastcam-Z is a pair of cameras located high on the rover's mast.