Exploring the final frontier isn’t the intimate experience it is on Earth. Scientists can’t get their hands dirty on the surface of Mars or Pluto. Rovers help on Mars, but for most planets – all scientists have to go on are images.
In Pluto’s case, NASA’s New Horizons spacecraft soared past at a distance of about 7,750 miles. Despite the distances and not having all the data yet, scientists have made incredible discoveries. From floating nitrogen ice glaciers to evidence of flowing liquids in Pluto’s past. All of this made possible just by looking at imaging data from New Horizons.
Two members of the New Horizons team recently wrote about the challenges with exploring a distant world. “After flyby our challenge was to piece together the geological history of Pluto’s surface – that is, to determine what processes have formed and modified each terrain, and when these processes occurred relative to one another,” writes Oliver White, a postdoctoral research in planetary science at NASA Ames Research Center.
To piece together a map of Pluto, scientists rely on New Horizons’ instruments. Specifically, the Ralph/Multispectral Visible Imaging Camera (MVIC) and the Linear Etalon Imaging Spectral Array (LEISA). By seeing how Pluto appears in different spectrums, scientists can tell what material lies on the surface.
A couple of days ago, I wrote about Pluto’s Halo craters. The LEISA instrument showed bright methane ice distributed on the crater rims and walls. While water ice rested on the crater floors.
White explains how imaging data opens up their understanding of Pluto. “Knowing the composition of a unit helps constrain what physical properties if has and, therefore, how it likely formed and was modified over time. The compositional data are the closest we have to possessing an ice sample from each of the different terrains on Pluto.”
White created an intricate map of Pluto’s informally named Sputnik Planum. Each color on the map represents an area with different geological terrain.
This map focuses on the texture of Sputnik Planum’s terrain. From the mountains bordering the left edge of the vast plain to the bright, cellular plains at its heart. Maps such as these paint an immediate picture of Pluto’s varied terrains. And better show the nuances of Pluto’s terrain than a traditional image. Here’s a normal image of the same area.
Today, White is busy mapping the rest of Pluto’s encounter hemisphere (the side New Horizons saw when it soared past).
Ross Beyer, a planetary scientist with the Carl Sagan Center at SETI Institute and NASA Ames Research Center, touched on how maps and mosaic images of Pluto take shape. When scientists received the first image dump from Pluto, they began creating a control network.
Beyer uses a crater as an example. If two images have the same feature (in this case a crater) scientists mark the spot. They do this across many features on tons of images. Before long, they have a lot of control points. Then, scientists toss them into a computer program to select and track the points they deem most important.
“Once we have a rich control network made up of points from all of the images we can measure, we can use a computer to perform something called a “bundle adjustment solution.” This action takes those points, and some information from the spacecraft about approximately where it was and where it was pointing when it took each image, and creates a “solution” for each image that correctly places it. This allows us to create mosaics and maps from the images. That is the key to knowing that image A is next to image B, for example, or that image C is higher resolution than either of them and is located within image A.”
And that’s how the beautiful mosaics of Pluto are created. It’s also how they overlay data from other instruments onto the images.
You can’t beat exploring a new place by hand, but it’s pretty damn incredible what scientists can do with just cameras.