Are we alone in the universe? Some scientists are attempting to answer this question by exploring the closest planet most similar to Earth – Mars.
There are two main ways of studying the surface of Mars. Rovers, like Opportunity and Curiosity, are currently operating on the planet. The other method is satellites.
Dr. Deanne Rogers, assistant professor in the Department of Geosciences at Stony Brook University, uses satellites to search for signs of past Martian life.
The sun shines light on Mars, which absorbs and reflects different wavelengths of that light, both those humans can see and those that they cannot, like infrared and ultraviolet light.
Satellites, in orbit around Mars, can take pictures of the planet’s surface in both the visible spectrum and infrared spectrum. With these pictures, scientists like Dr. Rogers can detect different minerals.
For instance, Martian soil is rich in iron, which is red in appearance due to the element’s reflection of red light. It gives the planet its recognizable red hue and is easy to detect in the visible light spectrum. However, most other minerals are not as easy to detect this way and require infrared technology.
Different minerals will absorb and reflect different wavelengths when exposed to light. Just as iron reflects red while absorbing other wavelengths like blue and yellow colors in the visible spectrum, it also absorbs and reflects different wavelengths of light in the infrared spectrum. Though satellites can detect infrared, infrared refers to light with wavelengths longer than human eyes can detect.
As Cong Pan, a graduate student in Dr. Rogers’s lab, describes, a tool on the satellites called a spectrometer analyzes the images and reports which wavelengths are reflected by the minerals on the Martian surface.
Similarly, scientists determine which wavelengths are reflected by minerals of interest by analyzing them in spectrometers in their own laboratories. By comparing the known analyses of specific minerals with the images of the Martian surface, researchers can pinpoint areas of the Martian surface that contain the minerals they are interested in.
Locating specific minerals is important because different minerals distinguish different types of environments.
When certain types of salts, like sulfates, are detected, it likely means that water was present at one point, but was shallow and evaporated quickly. This left behind an acidic environment not suitable for life.
This led researchers, like Dr. Rogers, to seek out deeper regions of the Martian surface. Deeper areas likely allowed water to pool and evaporate more slowly, potentially preserving life.
As described in Dr. Rogers’s recent Nature Geoscience paper, interest is growing in the McLaughlin Crater. McLaughlin is one of the deepest craters on Mars. Spectrometer data show mineral deposits like iron, magnesium and carbonates that may point to an environment with pooled water, such as a lake.
There does not appear to be evidence that water drained into the crater from the surface. Therefore, it has been proposed that the water arose from the ground. If Mars at one point had a significant supply of groundwater, it could mean that life may have existed in the subsurface where the water originated.
Fifty percent of Earth’s biomass exists below the surface and Mars could have had a similarly significant proportion of life living underground. McLaughlin Crater not only has the right depth and the right types of minerals, it also has structures that suggest landslides may have occurred, potentially preserving any remnants of life that might have existed subsurface.
So what is the next step?
To more fully understand McLaughlin Crater, scientists need more detailed analyses of soil samples and the current rovers cannot do this. Therefore, NASA has plans to land another rover on the Martian surface in 2020, a rover with more sophisticated, analytical capabilities. Additionally, future exploration plans may include bringing soil samples back to Earth.
NASA has not decided the destination of the proposed 2020 rover. Many researchers submit applications for the rover to land in their region of interest. Scientists like Dr. Rogers are petitioning for McLaughlin Crater, while others are petitioning for different areas, like the Columbia Hills.
Dr. Rogers explained that finding life on just one other planet would mean that life probably exists on many others. If many planets support life, then the odds of finding intelligent life in the universe becomes more likely.
So, are we alone in the universe? Maybe not for long.