The existence of water on Mars was uncovered in 2008 when NASA’s Phoenix Mars Lander found evidence of water ice beneath the planet’s surface. But that discovery only led to more questions.

One of these questions — about when water was present on Mars — resonated with a pair of Syracuse University scientists. Suzanne Baldwin, a professor of earth sciences, and Joseph Kula, a research associate and corresponding author for the study, began the process of answering the unknown more than two years ago.

Baldwin and Kula’s work is part of the New York Center for Astrobiology at Rensselaer Polytechnic Institute, which in turn is part of the NASA Astrobiology Institute. Their findings were published in an issue of Earth and Planetary Science Letters on Oct. 15.

The team’s research has centered around the mineral jarosite, a mineral with unique characteristics.

‘If you see it, you know something has changed,’ Kula said. ‘You had a water source somewhere, and then for it to be still present in the rock millions of years later, billions of years later, that environment had to stay relatively dry. So it can date the time since water was last there.’  

The potential of this trait was recognized when jarosite, which has already been seen on Earth, was discovered on Mars in 2004, Kula said. A Mars Exploration Rover called Opportunity found the mineral in rocks on the planet’s surface. From this, a foundational premise arose: If it is possible to date jarosite on Earth, jarosite-bearing samples from Mars may be able to be dated as well.

While the concept is simple, the process of realizing it is not.

In preparation for samples from Mars, Baldwin and Kula assumed the task of determining whether the mineral could first be dated on Earth. The jarosite they studied came from Chihuahua, Mexico, and was held in the Smithsonian Institution’s Department of Mineral Sciences, Kula said.

Using professor Baldwin’s noble gas geochronology lab located in the Heroy Geology building, the team performed slow, careful heating experiments to determine how old the mineral was and the conditions of the planet’s surface during its formation, Kula said.

Kula said their experiments worked surprisingly well. Results suggest the noble gas argon, which concentrates over periods of time in jarosite, can be preserved in the mineral for 4 billion years, according to an Oct. 19 SU News release.

‘Based on argon diffusion, it looks like, at surface conditions over long time scales, jarosite is a stable chronometer,’ Kula said. ‘It preserves its age of formation.’

The team is continuing its research, experimenting on samples from the Big Horn Basin in Wyoming, where jarosite formed less than 50 million years ago, according to the release. The research strives to approximate when the mineral formed and determine a timeline indicating the rate of when the environment transitioned from wet to dry conditions.

The team’s work provides a structure for long-term study.

‘The goal is to understand what we can date in terms of these minerals that are also found on Mars, so that when we go and get samples returned, we know what to do with this stuff, we know how to interpret it,’ Kula said.

There is speculation as to when those samples will return to Earth, ranging from five to 15 years. Within the next two months, NASA is prepared to launch Curiosity, a rover five times the size of Opportunity that is expected to land on the surface of Mars in August, according to the NASA website. Scientists hope Curiosity will be able to bring back jarosite-bearing samples for testing.  

Paul Tomascak, an associate professor of geology and geochemistry at State University of New York at Oswego, said the main importance of the study is that it takes a more proactive stance of being ready for when the samples get back.

‘One of the problems with sample returns is that it’s not going to be a lot of sample, it’s going to be a very selective sample from a very isolated spot,’ he said.

Kula said although studying jarosite is a step in the right direction, there is still a lot to learn.

Said Kula: ‘It’s very similar to Earth, where you can get people talking about it like we know how everything works, but there’s a ton of stuff we don’t know anything about.’

ebianchi@syr.edu

Published on October 26, 2011 at 12:00 pm