Planetary Orbital Surveys Using A Tetracorder
In Star Trek, the intrepid explorers use a handheld device called a tricorder to sense, record and compute environmental data. But scientists in the real world have one-upped our fictional friends with the invention of Tetracorder.
Tetracorder takes imaging spectrometer data – or patterns of light emitted or reflected from an object – from huge swaths of land, sea and sky and quickly analyzes it. In a new paper, published in the Planetary Science Journal, researchers explain that Tetracorder analysis has taken another developmental leap that allows quick production of mineral maps. The paper also reports on field research indicating that the technology can be deployed on a rover to help guide autonomous exploration.
Planetary Science Institute Senior Scientist Roger Clark is lead author and PSI Senior Scientists Eldar Noe Dobrea and Amanda Hendrix and PSI Laboratory Technician Neil Pearson are co-authors.
A dozen researchers, led by Clark, have been working for decades to develop and refine this technology. It is currently being used by NASA’s Earth Surface Mineral Dust Source Investigation, or EMIT, instrument onboard the International Space Station to map minerals, dust, ice and snow, water and more on the Earth. EMIT was recently granted a mission extension.
“Back in the 1980s and 90s, when we were starting to get really good spectra of other planets, researchers would spend weeks, if not months, analyzing a handful of spectra,” Clark said. “Then imaging spectrometers came along. So instead of a few dozen spectra, we would be getting millions of spectra per minute. The whole game had to change in order to be able to analyze this amount of data.”
A Tetracorder color map (left) showing a mountain snow scene in the Chile-Argentina border (natural color on the right) made from data collected by EMIT. The snow shows no detectable melting at higher elevations (magenta), but melting at lower elevations (blue). Also shown are sediments in water from the snow melt. Credit: Clark et al., 2024, PSJ Tetracorder paper
Tetracorder autogenerates maps of hundreds of compounds before synthesizing many into colored maps with multiple compounds denoted on each. These can include maps of water and impurities in the water, organic compounds and minerals and their grain sizes, for example.
“It is now easy to define what compounds one wants on a particular map for a specific science problem, and then have it auto-generated as new data arrives,” Clark said.
Tetracorder was recently used to find water and hydroxyl on the Moon. It will also be used to harvest rich information about Europa, Jupiter’s ocean moon encapsulated in ice, from data returned by the Mapping Imaging Spectrometer for Europa, or MISE, instrument onboard Europa Clipper, which launched Oct. 14, 2024.
A Tetracorder map of the Moon showing water absorption areas (with an Earth-based image of the Moon in the center right to establish the boundaries of this map). The different colors represent different shapes of the water absorption from which scientists can infer the presence of specific minerals. The crater Copernicus is above center with water and hydroxyl in the melt sheet from the crater impact. At upper right is the Apollo 15 landing site (labeled AP15), and below center are the Apollo 14 and 15 landing sites (AP14, AP15). All three landing sites are in water poor areas. The Apollo 15 site showed they were the higher water content rock in the Apennine Mountains. Credit: Clark et al. 2024, PSJ lunar water paper.
“One major thing MISE and Tetracorder will help us determine is Europa’s surface composition,” Clark said. “This will allow help us determine Europa’s habitability. There’s evidence for acid that’s been frozen, such as sulfuric acid, but that would be hostile to life. We also expect salts to come up from an ocean below. A small amount of salt in the ocean would be hospitable to life, but too much salt might reduce habitability.”
The results from Clipper can also be used to target best locations for a future lander, and a rover with an imaging spectrometer and Tetracorder analysis could explore the details at a landing site.
The PSI portion of this work is funded by a NASA EMIT subcontract to PSI from the Jet Propulsion Laboratory, a NASA SSERVI TREX award (80ARC017M0005) and NASA Europa Clipper projects.
Astrobiology
