The Valles Marineris, the largest canyon in our solar system, appears as a dark scar across the copper face of Mars. The theory that the gullies in the valley are being morphed by water flow has been recently been disproven by scientists at Johns Hopkins University Applied Physics Laboratory (APL). Image credit: NASA.
Jorge Núñez and his team of scientists at the Johns Hopkins University Applied Physics Laboratory (APL) have crushed one of the most exciting theories in our solar system: that liquid water flows on Mars.
After observing years of morphological changes in the Martian gullies of the Valles Marineris, many scientists hypothesized water flow to be the cause. But the APL team’s research, recently published in Geophysical Research Letters, proves that this is not the case.
Núñez is the lead planetary scientist of the APL project and the principal author of the research paper. A few years ago, while most theorists were searching for possible sources of water in the gullies using NASA’s High Resolution Imaging Science Experiment (HiRISE), Núñez came up with the idea to investigate the gullies’ mineralogical composition using NASA’s Compact Reconnaissance Imaging Spectrometer for Mars (CRISM).
Núñez primarily studies the geologic history of planetary surfaces and has in-depth knowledge of analyzing geological spectrum data. His idea was look into the content spectrum of the gullies to see if their mineralogy even suggested the current presence of flowing water. And it turns out it doesn’t.
Núñez explains how he and his team debunked one of Mars’ most exciting scientific possibilities:
How did your research differ from other scientists who were looking into the water flow theory in these Martian gullies?
When we came into the picture, a lot of this work looking at gullies was based primarily on morphology using HiRISE, or the Europeans using the context camera, as well as modeling potential stability of water and at atmosphere. But not a lot of people had looked at the composition. So our thought was, well, what if maybe looking at the minerality if it’s even possible [to have water] in these gullies.
We looked at high-resolution CRISM images of these gullies to see if we could extract compositional data.
CRISM data and spectrometer data can be very complicated to work with. So if you’re not as familiar with the instrument the data sets, it might detract some people from working with that data set.
With HIRISE you are looking at an image, and with that image you can do morphology and stuff. But with CRISM, instead of just one image, you’re dealing with basically hundreds of images to generate what is called a data cube, where you can extract a [composition] spectrum. You have to have some kind of knowledge about the spectroscopy, or minerality, to interoperate what the squiggly lines mean.
How were you able to determine the composition within the gullies with the CRISM images?
There is a little bit of processing you have to do with a CRISM image. You have to correct for the instrument artifact, you have to correct for atmospheric effects of the planet—Mars has a dynamic atmosphere that changes per day, you could have a slightly thicker [atmospheric] density, or dust in the air, and all of that affects the spectrum that we’re collecting with the instrument. So you have to be able to have very well calibrated, as well as coordinated data information to be able to correct for those kinds of effects.
We basically developed these new corrections and generated this new product, which is called Map Projected Targeted Reduced Data Record, or MTRDR. What it does is correct [CRISM images] for all of these [interferences] and allows you to overlay it, for example, on top of a HiRISE image, so that you not only get your spatial information, but also your composition information, which are really well correlated.
That allowed us to be able to determine what kind of mineralities are there, but also take in the relationship: Are these minerals that are formed within the gullies, or is it something that existed previous to that?
What were you looking for in the minerality that would suggest water flow?
Clays are a really good indication of persistent water activities. You need enough time for the water to interact with the rock to make these chemical alterations.
We started seeing clays, which was really exciting. But when you looked at it up close, and once you started correlating not only the compositional data with CRISM, as well as the location of these clays, but when you tie it in with the HiRISE data and the context imager, you can see pretty clearly that the clays were just being eroded out. It’s not something that had been formed as a result of liquid water flowing over it and carving.
They were ancient clays.
So that was a bummer. [Chuckles.]
Do you still think we will discover liquid water on Mars?
Besides being a planetary scientist, I’m also an astrobiologist. I’m interested to see if Mars was habitable or is still habitable, so there is hope that maybe we might be able to find evidence of life or that there was life on Mars. So, I am still holding out hope.