Funny Name, Serious Science: The Goniometer

Frost at the Viking 2 lander site in Utopia Planitia, May 1979. Weathered rocks like these require careful measurement to craft an accurate understanding of their history and geology.   Source   :  NASA

Frost at the Viking 2 lander site in Utopia Planitia, May 1979. Weathered rocks like these require careful measurement to craft an accurate understanding of their history and geology. Source: NASA

by Kathleen Hoza, Systems Engineer & Rhae Adams, VP of Strategy & Business Development

First Mode and Western Washington University (WWU) were recently awarded a contract by NASA to develop unique geological research technology that will enhance understanding of the surface of Mars. The proposed instrument, a goniometer, will quantify how observation of rocks at different angles impacts the resulting measurement. The work is funded through NASA’s Planetary Science Division under its “Solar System Workings” (SSW) Program.

What is a Goniometer?

3D Goniometer Rendering. Source: Peter Illsley, First Mode

3D Goniometer Rendering. Source: Peter Illsley, First Mode

At its core, a goniometer (pronounced go·ni·om·e·ter) is a fancy name for a tool that either measures an angle or helps position an object at a very precise angle for measurement. If you used a protractor in grade school to measure angles, you used a simple version of a goniometer. When measurements need to be extremely precise, or they need to occur in three dimensions, the instruments tend to get a bit more complicated, but the idea behind them is the same.

In this case, First Mode and WWU are building a 3D-goniometer (pictured) to measure rock samples as they would be encountered in the real world (i.e., not prepared as a two-dimensional sample). This particular instrument will allow a few things to occur.

  1. A light source can be positioned with a high level of accuracy on one of the moveable arcs.

  2. A detector can be positioned with equal accuracy on the other moveable arc.

  3. A three-dimensional sample can be inserted into the instrument as-is, rather than a sample that must be prepared or sliced.

When put together, this instrument will enable spectral observations of rock samples at different angles. To read more about spectroscopy as a science, check out our post here.

Why is this work important?

A viewing geometry is defined by an emission angle  e , incidence angle  i , and azimuth angle  ∅ . Phase angle  g  is the angle between  e  and  i.  Source: Kathleen Hoza, First Mode

A viewing geometry is defined by an emission angle e, incidence angle i, and azimuth angle . Phase angle g is the angle between e and i. Source: Kathleen Hoza, First Mode

Fundamentally, geology is science concerned with what we can learn from the rocks, soil, and processes that form any terrestrial planet or natural satellite, including Earth, Mars, or the Moon. The more we can learn about the composition, age, and history of a rock, the better we can understand past climates, evolutionary history, and even the location of valuable minerals.

While Earth-based methods of geology include highly precise laboratory techniques, on other planetary bodies, we lack infrastructure such as climate-controlled space, heavy lab equipment, and people on the surface (for now!). Instead, we rely on our robotic emissaries to capture scientific data via their instrumentation and send it back to us here on Earth.

When we take scientific measurements, the details become critical. We are faced with many bold questions as we investigate Mars. Was flowing water present on Mars in the past? Could it have hosted life? What happened to it? In the face of these important questions, we must have a high degree of confidence in the data that informs our answers. It isn’t the kind of thing you want to be wrong about!

One of those critical details is the viewing geometry (pictured). Measurements of rocks, particularly those that have been weathered over time, are known to be influenced by the angular positioning of the detector (the rover) relative to the target material, but that influence has never been fully quantified. You can think about it like taking a picture with your iPhone — your picture is going to turn out very different as you move, tilt, and interact with your light source (the sun), your subject, and your detector (iPhone).

Once the goniometer is built, it will be used to characterize a representative suite of Martian analog rocks with different compositions, textures, and degrees of alteration. This data will be used by researchers at WWU and NASA to develop a library against which geologists can compare spacecraft data from Mars. The library can help scientists spot subtle variations in measurements and detect key weathering patterns that might otherwise be overlooked.

For example, microns-thick layers of amorphous silica, which could indicate the past presence of water, might not be detectable using standard techniques, but they create observable differences when measurements are taken at different angles.

Who will benefit?

By working with NASA and WWU, First Mode hopes to enable a wide range of scientific discoveries. To ensure the best tools are in the hands of geologists and scientists around the globe, this new, automated instrument design and accompanying custom software package will be publicly released upon completion. We hope this makes the process of efficient data collection easy, not just for this study, but for students, scientists, and institutions working to understand our universe across the planet.

For more information, be sure to sign up for our newsletter on our homepage, or reach out directly!

InsightsRebecca MacLeod