HiWish upon a Mars
by Emily Lakdawalla on November 15, 2012
Mars Reconnaissance Orbiter — the most recent arrival to Mars orbit — carries what is arguably the greatest camera ever sent beyond Earth orbit. Called HiRISE, it can capture color images with resolutions as high as 25 centimeters per pixel. Here’s a circumstance when using Imperial units makes sense: that is just about one foot. Look at a full-resolution HiRISE photo, and each pixel covers about exactly the amount of space that your feet would span if you were standing on the surface of Mars.
To get a sense of how great these images can be, check out the HiRISE view of Curiosity landing, or these gorgeous lava swirls, or a favorite Martian feature called White Rock, or north polar avalanches in action.
There’s one more thing that makes HiRISE special. Unlike any of the other spacecraft cameras I’ve talked about so far on nerdist.com, HiRISE is one that you, yes, you, can command to take photos of your chosen spots on Mars. Why? How?
Because of its extremely high resolution, HiRISE images only cover very small areas, and there’s no way that the spacecraft will live long enough for HiRISE to photograph all of Mars. In fact, it’ll just cover a few percent of the surface. So you have to be choosy, and the HiRISE team has invited the public to participate in the choices. The program is called HiWish, and it’s accessible to professionals and amateurs, grownups and kids. I’ve made 10 or so requests, and gotten five back. Here’s my most recent HiWish image:
Anybody can make a HiWish, though to be successful, you have to do a little homework. Here’s the HiWish website. A while ago I wrote a post explaining how the process works. In brief: the HiWish website shows you a map of Mars, and when you zoom in enough, they show you red boxes outlining areas where HiRISE images have already been taken. They also show you white boxes, which are other people’s HiWish targets. Clicking anywhere on the map plunks down a new white box; that’s all you have to do to select the area you want to photograph.
But you’re not quite done yet. The HiRISE team also wants to know why you think that’s a good spot. “It looks cool” is not a particularly good reason, nor is “there’s an alien base there.” They want a scientific justification. You may say: but I’m not a scientist.
Oh yes, you are!
Are you curious? Do you want to know why things happen? Do you investigate things you’re curious about? You’re a scientist.
Here are short versions of some of the explanations I’ve used when I make HiWish requests:
- This feature looks like a very fresh crater.
- The wall of this crater seems to have exposed layers.
- There are lots of HiRISE images covering the western parts of this canyon, but the coverage is sparse in the east. This image could be used to compare to the other ones. Also, other images in this area are just gorgeous, and I want to see more.
- An earlier image in this spot shows a crater that formed in 2006. I would like a second photo to see if the crater ejecta has faded.
- There is a HiRISE image of this spot that shows cool topography. I want a second image of the same spot from a different angle so we can see it in 3D.
One thing that I’ve found works very well is to start by browsing lower-resolution pictures. Mars Reconnaissance Orbiter has another camera, the Context Camera (or CTX), which takes images at lower resolution than HiRISE (6 meters per pixel). Each CTX image is huge, so over the course of Mars Reconnaissance Orbiter’s six-plus years at Mars, CTX has wallpapered the majority of the planet with images already. Below the HiWish map interface, you will find a checkbox next to an orange word, “CTX”. Click that and the map will show you the footprints of CTX images. Clicking on each orange Google Map pushpin will open up a text balloon that contains a link to a web page where you can browse that image. If you see something really cool-looking in a CTX image, but the CTX image doesn’t have quite enough detail for your taste, that’s a good spot for a HiWish request. Explain what you see in the CTX image to justify the HiWish request.
I’ve talked with Alfred McEwen (the HiRISE principal investigator) about this program, and he’s actually been disappointed with how few people are using it. When I try to get people to use it, they usually tell me they don’t want to try because they don’t figure they can succeed. That’s just laziness. This isn’t a lottery; If you do better than clicking randomly, and write any kind of justification at all, you have a good chance of your choice being accepted. Go try it out!