Oxygen Isotope Forensics: Mars meteorite expert shares findings at La Jolla library lecture

To shine a spotlight on local, groundbreaking science and scientists, La Jolla Riford Library presents monthly Citizen Science Lectures, and hopes to continue them the first Tuesday of each month. While future speakers have yet to be booked, library science educator Callen Hyland said the plan is to bring advanced research to “curious, scientifically minded citizens.”

At the Aug. 1 lecture, UC San Diego scientist Robina Shaheen, Ph.D., (chemistry and biochemistry departments) spoke about solving the mysteries of the planet Mars with oxygen isotope forensics. At the lecture, everyone (from science enthusiasts who could identify meteorites by name and number to those admittedly trying to keep up) gathered in the community room.

Among the complex issues discussed at the hour-long lecture (punctuated with questions from the audience), Shaheen talked about the potential for sustaining life on Mars, how scientists use meteorites to understand chemical reactions and the future of Mars exploration.

She explained how scientists can take the oxygen isotopes (variants of a particular chemical element, in some cases, by weight) found on meteorites from Mars, measure the isotopic qualities compared to those found on Earth, and how the isotopes measure up in terms of the elements required for sustaining human life: Carbon dioxide (CO2), water (H2O) and oxygen (O).

“In order for life to exist, the planet would have to be in what is known as the ‘Goldilocks Zone’ where water exists in liquid phase, vapor phase and solid phase. We know if water is in the vapor phase, it becomes clouds and it falls in rain (liquid) or snow (solid). This is how water is purified and this is the hydrological cycle. In our solar system, we’re in a small window where life can exist,” she said.

“To understand the geology of Mars, and therefore understand if there ever was life on Mars or whether it could sustain life, we had to look at CO2, water and oxygen because these are essential ingredients for what we know about life on Earth. CO2 warms the planet, water facilitates biochemical functions and we need oxygen to breathe.”

Water exists in frozen caps on Mars’ northern and southern poles, and there are images of what may have been rivers or channels on the surface, but they are dry, she said.

Using atmospheric readings from NASA rover vehicles, such as Viking 1 & 2 (which landed on Mars’ surface in 1976), Shaheen said scientists have a better understanding of the isotopes found on Mars. “When meteorites land on Earth, we can look at their isotope makeup to confirm they are from Mars,” she said.

As for the future of Martian exploration, she said it’s possible there might be life buried under Mars’ ice caps, but that solar and galactic radiation would influence DNA production on the main surface. NASA plans to investigate further, via a 2020 mission to Mars.

Mars or Bust

According to NASA, “The Mars 2020 Rover introduces a drill that can collect core samples of the most promising rocks and soils and set them aside in a ‘cache’ on the surface of Mars. A future mission could potentially return these samples to Earth. That would help scientists study the samples in laboratories with special room-sized equipment that would be too large to take to Mars.”

Shaheen said the sample could not yet be brought to Earth because “We can’t take the risk. We have not discovered what type of microbe might be under the ice. It might be very aggressive because it is constantly exposed to radiation. It might be so resistant that we don’t have anything to handle it. So the sample would need to stay in orbit.”

She added that once instruments sophisticated enough are developed and ready “we can calculate how much carbon dioxide and water are in the ice.”

NASA information states, “The mission also provides opportunities to gather knowledge and demonstrate technologies that address the challenges of future human expeditions to Mars. These include testing a method for producing oxygen from the Martian atmosphere, identifying other resources (such as subsurface water), improving landing techniques, and characterizing weather, dust, and other potential environmental conditions that could affect future astronauts living and working on Mars.”