That’s why Goddard engineer Dr. Berhanu Bulcha has been working on a type of instrument called a heterodyne spectrometer that could zoom in on particular frequencies to definitively identify and locate water sources on the Moon. To function however, it would need a stable, high-powered, terahertz laser, which was prototyped in collaboration with Longwave Photonics through NASA’s Small Business Innovation Research (SBIR) program.
“This laser allows us to open a new window to study this frequency spectrum,” Bulcha said. “Other missions found hydration on the Moon, but that could indicate hydroxyl or water. If it’s water, where did it come from? Is it indigenous to the formation of the Moon, or did it arrive later by comet impacts? How much water is there? We need to answer these questions because water is critical for survival and can be used to make fuel for further exploration.”
The new tool would function by detecting spectra or wavelengths of light in order to reveal the chemical properties of matter that light has touched. Hydrogen-containing compounds like water emit photons in the terahertz frequency range (2 trillion to 10 trillion cycles per second) between microwave and infrared. This means that scientists can measure the difference between a laser source and the combined wavelength to identify water molecules.
“The problem with existing laser technology,” Bulcha said, “is that no materials have the right properties to produce a terahertz wave.”