Researchers have found that Mars’s crust may be more complex and evolved than previously thought.
The early crust on Mars may have been similar to our planet’s original crust. Mars’s surface is basaltic, due to billions of years of volcanism and flowing lava on the surface that eventually cooled. Scientists had previously thought that the history behind Mars’s crust was simple, as the planet did not undergo full-scale surface shifts like the continents on Earth.
However, researchers have now discovered that areas of Mars’s southern hemisphere have greater concentrations of silicon than what would be expected in a purely basaltic setting. The presence of this chemical element had been revealed by space rocks that slammed into the planet.
The study titled, ‘An evolved early crust exposed on Mars revealed through spectroscopy,’ was published in the journal Geophysical Research Letters.
How did Mars’s crust form?
Valerie Payré, Assistant Professor in the Department of Earth and Environmental Sciences at the University of Iowa and the study’s corresponding author, said: “There is more silica in the composition that makes the rocks not basalt, but what we call more evolved in composition.
“That tells us how the crust formed on Mars is definitely more complex than what we knew. So, it’s more about understanding that process, and especially what it means for how Earth’s crust first formed.”
It is thought that Mars formed around 4.5 billion years ago, but exactly how the planet was formed is a mystery. However, there are numerous theories on this.
One theory poses that Mars formed through a collision of rocks in space that, with intense heat, created a magma ocean. This magma ocean then gradually cooled, creating Mars’s surface that was thought to be predominantly basaltic.
Another theory argued that the magma ocean was not all-encompassing, and Mars’s first crust has an origin that would highlight silica concentrations different from basaltic.
Detecting silica concentrations
The team analysed data from the Mars Reconnaissance Orbiter for the planet’s southern hemisphere, which was previously indicated to be the oldest region according to research. Nine areas, such as craters and fractures in the terrain, were found to be rich in feldspar, a mineral associated with lava flows that are more silicic than basaltic.
“This was the first clue,” Payré said. “It is because the terrains are feldspar-rich that we explored the silica concentrations there.”
Although felspar has been previously found in other areas on Mars, further analysis showed that the chemical composition in those areas was more basaltic. The researchers were not deterred by this, however, and instead used another instrument called THEMIS, which can detect silica concentrations through infrared wavelength reflections from Mars’s surface. By using this data, the team confirmed that the terrain at their chosen locations was more silicic than basaltic.
Meteorites provide further evidence for these observations
Meteorites are also adding further credence to the team’s observations. Erg Check 002, a meteorite discovered in the Sahara, dating roughly to the birth of the solar system, shows similar silicic and other mineral compositions that the team observed on Mars’s surface.
The crust was also dated to about 4.2 billion years, making it the oldest crust on Mars to date.
Payré was mildly surprised at the discovery, stating: “There have been rovers on the surface that have observed rocks that were more silicic than basaltic. So, there were ideas that the crust could be more silicic. But we never knew, and we still don’t know, how the early crust was formed, or how old it is, so it’s kind of a mystery still.”
Future uses to understand Earth’s evolution
Although there have now been some insights into the origin of Mars’s surface, the history of Earth’s crust still remains unclear, as our planet’s original crust shifted for billions of years. The findings may be able to shed light on Earth’s origins in the future, however.
“We don’t know our planet’s crust from the beginning; we don’t even know when life first appeared,” Payré said. “Many think the two could be related. So, understanding what the crust was like a long time ago could help us understand the whole evolution of our planet.”
NASA funded the research, through the Mars Science Laboratory Participating Scientist Program and the Mars Odyssey THEMIS project.