The history of space exploration is marked by a handful of grand milestones. The Apollo 11 moon landing, the first space shuttle launch, and the Curiosity Mars mission. Like stars shining in the night sky, these events command the imagination of the public. But the space between these milestones is far from empty. The journey continues in the labs and offices of people whose work lie in relative darkness, but without whom we can never say even the most basic facts: that stars are burning balls of hydrogen.
Bryné Hadnott is one of those explorers. “More than just knowing what looks like, is there, I want to know what is actually there. There are many people who interpret images and say that’s a hill, or that’s a valley, which is interesting, but I want to know what that hill is made of, what that valley is made of.” As a doctoral student in the Department of Earth and Atmospheric Sciences, Hadnott is involved in two projects that seek to understand the material composition of objects in space.
Studying Hydrated Minerals
In the one project, Hadnott studies the temperature dependence of OH (oxygen-hydrogen) bands in hydrated minerals, which is vital in the spectrometry analysis of materials from space.
One of the primary methods of analyzing materials without physical contact, also called remote sensing, is spectroscopy. While there are many ways of performing spectroscopy, generally they all take advantage of how the electrons of atoms or electron bonds between atoms in a material absorb and release only specific amounts of energy in the form of light. When a significant frequency peak or band is detected in a spectrum of light from an unknown object, comparing bands from known samples can reveal the material composition of the object.
Straightforward as this may sound, under the extreme temperatures and pressures found in space, notable deviations occur to the otherwise established frequency bands of different compounds, making comparisons fraught with uncertainty. Such is the case for the OH bond, which is a sharing of electrons between an oxygen atom and a hydrogen atom. This type of bond is often found in certain minerals and can reveal a great deal about the material makeup of planetary bodies.
“If you have an orbiter around, say, Mars or Titan or Europa, you will be taking spectra that are not at room temperature and pressure. So we want to quantify [the shift and distortion] of the OH band. The idea is to help future remote sensing campaigns [interpret spectra more accurately],” says Hadnott.
“More than just knowing what looks like, is there, I want to know what is actually there. There are many people who interpret images and say that’s a hill, or that’s a valley…I want to know what that hill is made of, what that valley is made of.”
Hadnott completed part of the project at Cornell in collaboration with Alexander Hayes, Astronomy, while another part at the California Institute of Technology, with the help of George Rossman in the Department of Geological and Planetary Science. Their method involves crushing known mineral samples mixed with potassium bromide to form thin disks that are then shot with light, in the mid-infrared, to produce the spectra. They vary the sample’s temperature from -196 to 500 degrees Celsius, a range that encompasses most planetary temperatures. Then, they analyze the changes in the band positions.
As she continues with this project, Hadnott also wants to identify any fundamental relationship between temperature and bond length. This will advance the understanding of chemical bonds and may provide a more thorough explanation for the band shifts.
Designing a Fiber Optic Infrared Spectrometer
In the second project, Hadnott is developing a fiber optic probe for performing non-destructive analyses of material compositions. This study is oriented toward a possible mission to Titan, Saturn’s largest moon and the only known object other than Earth that shows strong evidence of stable liquid bodies on its surface.
Usually, accurate analyses of materials are done via mass spectrometry, which requires removing some sample from its native environment. Mass spectrometry, however, may prove to be prohibitive under certain scenarios, such as analyzing samples deep within a body of liquid, which is the case for Titan. It also requires additional equipment to extract the sample, which may fill up precious payload space on flight missions.
To design around that, Hadnott is developing an infrared spectrometer built into a flexible fiber optic cable. The cable has its own light source and can simply be extended until it sees the material of interest and collect an infrared sample from it.
One issue with infrared spectroscopy is that there is no direct linear relationship between the concentration of a compound and the intensity of its corresponding peak on a spectrum. Therefore, the project also investigates this relationship in order to enhance future remote sensing capabilities.
To simulate the conditions on Titan, Hadnott studies the probe’s performance by dipping it into known ethanol-methanol solutions, in gaseous nitrogen, cooled to about -180 degrees Celsius. “It’s quite a setup,” she says, with test tubes of ethane-methane nested in successively larger beakers of nitrogen, which is finally nested in a large Dewar tank of liquid nitrogen.
The project is collaborative with Robert Hodyss and Mike Malaska at the Jet Propulsion Laboratory.
Space or Earth?
During her undergraduate years at Washington University in St. Louis, Hadnott worked on a Mars analog project. The project simulated the analyses carried out by the celebrated Curiosity rover on Mars rocks. It covered methods including reflective spectroscopy, mass spectroscopy, electron microscopy, and x-ray diffraction, all of which corresponds to devices found on Curiosity or orbital data. Each of Curiosity’s instruments has a twin on Earth, and the instruments are calibrated with Earth materials that are analogous to those found on Mars.
She also did not forget about Earth. Hadnott’s undergraduate work led her to apply her knowledge of remote sensing to the New African Green Revolution project at the University of Vermont. There, she studied satellite images of Malawi to determine the relationship between precipitation and vegetation cover and whether a fertilizer subsidy program in 2005 affected that relationship.
But it is Hadnott’s journey into space exploration that may be the most fascinating. Astronomer Edwin Hubble once said, “No one should go into [astronomy] without a calling.” Hadnott began her undergraduate studies majoring in Art, drawn by the beauty of images, which “really spoke to me.” But then she saw images of light spectra and was mesmerized. “It was amazing, it was so artistic; you’re literally looking at light, how it changes as a function of wavelength. There is something about that technique that really clicks in my brain.” She answered that call and became a geochemist, and now, thanks to people such as Hadnott, we can shed a bit more light into that dark night sky.