“What we are doing is like detective work,” says Richards, who has a history working in mineral prospecting.
“We are gathering evidence of potential mineral deposits using satellites and other data sources; each satellite gives us a further understanding. We then continue to investigate these hotspots using various satellite methodologies including reconfiguring satellite data bands to identify the distinct signatures of specific minerals and build their reflectance profiles.”
The satellites the team uses include Sentinel-2, Landsat-8, Hyperion and Prisma, all of which were launched and are maintained by various governments.
The satellite images are hyperspectral. This means they capture the response of a material to ultraviolet light. By examining what bounces off the light, geologists can build a reflectance profile of the minerals on the surface. This may be a mineral alteration in the rock that could be caused by heat pressure, temperature, fluid fluxes or human effects.
“The hyperspectral imaging is on a per-pixel basis and allows us to do this through different combinations of spectra and band ratios. The pixels differ by satellite, what size they are, and by what wavelength of light you are looking at,” explains Richards.
Improvements in computer technology, memory, RAM (random-access memory), and software mean the images can be manipulated better and the data reconfigured.
“It also means we can utilise data that has been publicly available to us for decades in a much more meaningful way. This gives us a chance to find minerals in each one of the bands,” she adds.
The benefit of using hyperspectral imaging with rocks is that many rock profiles have already been documented by the US Geological Survey and NASA. There are even hyperspectral images from the moon.
In addition to the images, Richards and her colleagues are also analysing rocks taken from satellite hotspots under a microscope and at the nanoscale using various types of electron microscopy. Together this information helps them discover the fingerprints of certain rocks in both regional and local satellite data.
Other data such as geological maps, geophysical data and information from websites such as Mindat, which all hold a wide variety of data on rock samples, add another layer of information to their understanding of complex geological environments.
The data is combined in an algorithm, which Richards is honing with the university’s ai.sys research group to identify things in the data that would otherwise be missed because it is so complex.
“The AI helps us pick out hotspots in the images and data. It is designed to find a target, essentially,” she explains.