There are thousands of beautiful images of and from the surface of Mars. In this episode we talk about how and why these images are taken by rover photographers. From the taking images in black & white images verses color to church glass, how we study Mars through photography is fascinating.
Special thanks to Emily Lakdawalla, Melissa Rice, Nicole Schmitz and resources from KMRE – Spark Radio & Western Washington University
Image Courtesy of NASA
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[♪ Klaus Wunderlich playing Popcorn ♪]
Narrator: Hello and welcome back to spacecraft chronicles, a show where we explore stories of past, present, and future space missions. I’m your host, Regina Barber-Degraff, an astrophysicist and Mars enthusiast. This episode centers around photography and imaging on Mars. How has Mars been viewed in the past?
Humans have been interested in the Mars surface for hundreds of years. Mars was mapped once telescopes improved. In the late 1800s, many astronomers made more detailed maps, and some even jumped to conclusions about canals and alien civilizations.
By the mid 1900s, most of the astronomical community had realized that these canals were optical illusions, which was a huge disappointment for those who dreamed of Martians.
The first images of the Mars surface came from Mariner 4, a car-sized NASA spacecraft that flew by the planet in the summer of 1965. The first images from the Mars surface came from the Viking 1 Lander in 1976. Since then, NASA has made great advancement with the Pathfinder rover in the 90s, the Spirit and Opportunity rovers in the early 2000s, and the Curiosity rover exploring Mars today.
The future Mars 2020 mission, mentioned in a past episode, is a rover with Mast-CamZ to perform color, panoramic, stereoscopic (or 3D), and zoom imaging.
The first and foremost challenges in imaging are money and data. The average distance between Mars and earth is 140 million miles. So, communication between NASA and the rovers is limited in terms of speed and storage space.
Emily Lakdawalla, senior editor, and planetary evangelist for the Planetary Society, explains.
Emily: There’s something about people who have cameras on spacecraft. They don’t necessarily release all the images right away. They like to hang on to them for a little bit.
There are a couple exceptions to that, though. There are people who are really good about releasing images quickly. We’re here for this Mast-CamZ meeting. Jim Bell’s one of the better actors in that arena. So, we’re going to see all those images from this rover right away.
Narrator: Right. And it’s actually normal, right? This rover right now, Curiosity, does publish these images right away.
Emily: Most of them.
Narrator: And to the public within a week or something, I believe?
Emily: Most of the images are published as soon as they hit the surface. All of the ones from the navigational cameras, the hazard-avoidance cameras, and the Chem-Cam, the remote micro-imager, and the hand-lens imager.
All of those get sent to the web almost as soon as they hit earth. Only the color cameras on the mast; they hold those for a day before they release them. But it won’t be true for Mast-CamZ. For the next Mars rover, they’re going to release them right away. It’s going to be awesome.
Narrator: Tell me something about Mast-CamZ. I know it’s the next camera that’s going to go on the next 2020 mission. It’s slightly different from what we have now. Tell me what we have now.
Emily: What we have now is an instrument called Mast-Cam, that’s on the Curiosity rover. The Curiosity cameras flew with one zoomed in and one zoomed out, and so you have two different-sized eyes on the camera. What that means is that you can’t do proper stereo imaging. It’s sort of compromised that way. Mast-CamZ is going to fix that.
Narrator: The Z is the zoom?
Emily: The Z is the zoom. Moreover, the two cameras are going to be 100% identical, so that whatever you look at, you can see it with your left eye and right eye, and it’ll be in stereo, and it’ll be in color, and it’ll be awesome. So, all of the rovers that have ever been sent since Sojourner, all of the landers and rovers have had these stereo cameras on them. So, you can see things in 3D.
The navigational cameras that were on Spirit and Opportunity, and also on Curiosity, they see the whole world in 3D, but it’s black-and-white. So, people are always like, “Where’s the color? Why did they send black-and-white imagers to Mars?”
There are good reasons for that. One of them is that you don’t need the color. They’re just for getting the lay of the land and figuring out the topography, so you know where to drive and where to put your instruments. The other reason is that color requires 3 times as much data as black-and-white does. So, you don’t waste color unless you really need it to understand what you’re looking at.
The science imagers do have color capability. But the ones that are just for navigating around Mars, they don’t have it. You’d be able to return fewer pictures from Mars total, in exchange for having that color. So, it’s better to be black-and-white.
Narrator: Even though black and white pictures are more cost effective, color imaging can be quite useful in studying the geology or Mars-ology of the red planet. Here’s NASA rover scientist Dr. Melissa Rice to tell us more.
Melissa: Color images, unlike a black-and-white image, not only give us some sense of what the landscapes look like, but it also gives us a sense of what the landscapes are made of.
A good example are the rocks on Mars that contain a lot of iron. Iron, when it rusts, turns a bright red color. Most of the iron on the surface of Mars is oxidized. But not all of the iron has been rusted in this way. Sometimes that iron, when it’s in minerals and the rocks and hasn’t been altered–hasn’t been oxidized yet, those rocks will not have the red color. Those rocks will look more brown or grey, and they will look different in color images from those red, rusty colors.
When we take pictures of rocks on Mars, and of landscapes on the horizon, we want to be able to see the various shades of red so that we can interpret where the rocks have been through different types of alteration.
Now, Mars– pretty much everything on the surface looks like some hue of reddish-orangish-brownish. That’s not really a very beautiful color palette to the human eye. But, we still like to get color images because we take pictures in wavelengths that are longer than what the human eye is sensitive to. These are wavelengths that are not in the visible range of light, but the near-infrared range of light.
In order for us to take a picture in near-infrared wavelengths, what we need to do is put filters in front of the camera lens that only let those long wavelengths of light through.
We can take pictures in those wavelengths, and that’s really useful because Mars (while it looks just reddish-brown to our eyes) is actually much more colorful in these near-infrared wavelengths.
I think if there were Martians who had evolved on the surface of Mars, looking at the colors of the Mars surface, they probably wouldn’t be sensitive to the same wavelengths of light as we are, because it’s not very useful to see everything as a red planet. But I bet you that they would have eyeballs that were sensitive to the near infrared wavelengths, and they would see a full spectrum of colors that we can’t even perceive.
Narrator: Another difficulty of taking photographs of another planet is getting those colors right. However, Nicole Schmitz, an engineer at DLR (the German airspace center) recalls an ingenious solution to this problem, hundreds of years in the making.
Narrator: For our listeners, let’s describe what a calibration target is, because it’s basically just this thing on the rover that has known colors and ….
Nicole: It has known, yeah, it has spots with colors, which have been calibrated in a lab on earth. So, we know exactly the qualities of these colors. We know how they look under the earth’s atmosphere. That means that, on Mars, we can also measure how they look like in a Mars atmosphere, and so we can generate true color images, basically.
But you also have the danger that they might degrade over time, that the colors just might change because of, for example, radiation exposure. We had one of the engineers in our team, who was tasked to solve that problem, or to come up with an idea. He did a lot of research on the internet and looked at previous designs, and he actually found out: glasses. Windows of churches. [Unintelligible] churches.
They have stained glass. They just don’t degrade over centuries. So, we have these old cathedrals in Europe and they have stained glass in many, many different colors. You can actually add several minerals to this glass and get every color you like. And they just don’t degrade.
Actually, the next Mars rover, the next European Mars rover, will fly to Mars with color pictures that are made of church glass.
[♪ Klaus Wunderlich playing Popcorn ♪]
Narrator: Despite the distance, dust, radiation, and any other thing that could go wrong, earth’s scientists have managed to take closeup color images of another planet entirely. These color images can tell us the composition of Mars’ surface, but they can also help people get a better feel for what it would be like to watch a sunset on Mars.
Here, again, is Dr. Melissa Rice.
Melissa: On Mars, the sky is red during the day. That’s because the atmosphere is full of this reddish Mars dust, the same red Mars dust that’s all over the surface, making the planet look red in general. That red dust is in the sky. We see it during the day, but right at sunset, that’s when we see just a little bit of blue sky, only when the sun is there. We wouldn’t know that without our color imagers on the surface of Mars.
So, I really like the fact that Mars has these dramatically different sunsets, because this is a different planet entirely. This is not the earth, not what we’ve experienced! This is a world where the sky is red during the day and the setting sun is blue. I hope that one of those first astronauts to see that on Mars is a poet.
Narrator: Thank you for listening to this episode and be sure to tune in next time for another space story. This episode of Spacecraft Chronicles was recorded at the Mast-CamZ team meeting at Western Washington University in the summer of 2016. Additional audio was recorded in Bellingham, Washington, in July 2017.
This show was produced, written, and edited by Taylor Raybold, Natalie Moore, Melissa Rice, and Regina Barber-Degraff. Special thanks to Melissa Rice, Emily Lakdawalla, Kjarten Kink, Nicole Schmitz, and resources from CamRE and Western Washington University.
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