[X] My Assistant

[elakdawalla]

In the past, unmannedspaceflight.com has provided a public service to debunk conspiracy claims by helping people locate and describe images related to the weird claim of the week. My favorite two examples of these were the "Sasquatch on Mars" and the "Puddles on Mars." In that spirit, I'm hereby providing links to images and other data related to this week's fun, originating with this Houston Chronicle story: "NASA photo captures strange bright light coming out of Mars", quoting a UFO enthusiast website. Alan Boyle followed up on it with this post that annoyed me, and one just now that has me intrigued, quoting Justin Maki as saying it's not a cosmic ray hit.

Phil Plait asked me about this and I took one look at it and said "cosmic ray hit." Here's the picture, right Navcam from sol 589:

If you compare the image to the left eye taken at exactly the same moment, there is no bright pixel -- this is diagnostic of an event that affected only one camera, so is most likely a cosmic ray hit:

Another thing that tells you it's likely a cosmic ray hit and not a bleeding pixel from something bright is the fact that pixel bleeding on Navcams happens in the horizontal, not vertical direction. Just check any Navcam image of the Sun, or this low-light image from sol 593 in which the sloping side of the RTG is overexposed and bleeding horizontally. By contrast, cosmic ray hits can be oriented in any direction, such as in this nighttime Navcam pic.

And I figured my debunking work was done, until someone pointed out to me that there's another right Navcam image, shot from a similar but not identical location, at the same time of day, pointed in roughly the same direction, that also contains a bright dot. Here's the picture, right Navcam from sol 588:

As with the sol 589 image, the bright dot is not in the Left Navcam frame taken simultaneously, although this time that fact is explained by the presence of a foreground butte blocking the field of view:


This dot is different from the other one. It is not extended vertically. It's just a dot, that overlaps more than one pixel. Still, I would be inclined to dismiss this as a cosmic ray hit (saturating pixels, in one eye and not the other) without extraordinary evidence to the contrary. There are interesting coincidences here that could lend themselves to an alternative explanation, such as a specular reflection from a bright object: both are on the horizon, seen in the same direction, at the same time of day. But there is another coincidence that has me skeptical: seen in right eye only of the Navcam. And the vertical extension of the bright pixel in the sol 589 image just doesn't make sense for a specular glint; that would extend horizontally, not vertically, while cosmic ray hits can make streaks in any direction. So I am still inclined toward cosmic ray hits and coincidence, but I'll admit to being less totally certain about that after seeing the sol 588 image than I was after seeing the sol 589 image alone. And now there's this from engineering camera lead Justin Maki, via Alan Boyle:

"Bright spots appear in single images taken by the Navigation Camera on NASA's Curiosity Mars rover on April 2 and April 3. Each is in an image taken by this stereo camera's right-eye camera [with links to the April 3 and April 2 pictures] but not in images taken within a second of each of those by the left-eye camera [again, with links to April 3 and April 2]. In the two right-eye images, the spot is in different locations of the image frame and, in both cases, at the ground surface level in front of a crater rim on the horizon.

"One possibility is that the light is the glint from a rock surface reflecting the sun. When these images were taken each day, the sun was in the same direction as the bright spot, west-northwest from the rover, and relatively low in the sky. The rover science team is also looking at the possibility that the bright spots could be sunlight reaching the camera's CCD directly through a vent hole in the camera housing, which has happened previously on other cameras on Curiosity and other Mars rovers when the geometry of the incoming sunlight relative to the camera is precisely aligned.

"We think it's either a vent-hole light leak or a glinty rock."

Anybody got anything else to add? Other images of this spot? Where is the spot on the map, exactly? I can (and have) drawn lines on Joe Knapp's map but I'm not convinced I understand the geometry precisely enough to want to say anything about where any putative reflective object would be.

[jmknapp]

My triangulation could easily be 1 degree off. The direction of the boresight (center of image) is pretty reliable (as reliable as the SPICE kernel anyway) but to get the direction of the bright pixels I just counted pixels from the center assuming a uniform field of view of 45.33° and that the rover was level (which it fortunately was to within about a degree). So any lens distortion could throw it off too. It could be done more precisely if warranted, BUT how about this argument: if it was some kind of specular reflection that was so sensitive to direction that one NAVCAM saw it but the other didn't, and it was 176m away as Gerald figures above, then a 42 cm shift in baseline (0.13°) is the difference between seeing and not seeing. The sun for its part moves 0.13° in about 45 seconds. So then what are the odds that the thing would be seen twice on different sols from different positions? Pretty low right? Therefore by Ockham's Razor it's not a reflection.

[testguru]

My triangulation could easily be 1 degree off. The direction of the boresight (center of image) is pretty reliable (as reliable as the SPICE kernel anyway) but to get the direction of the bright pixels I just counted pixels from the center assuming a uniform field of view of 45.33° and that the rover was level (which it fortunately was to within about a degree). So any lens distortion could throw it off too. It could be done more precisely if warranted, BUT how about this argument: if it was some kind of specular reflection that was so sensitive to direction that one NAVCAM saw it but the other didn't, and it was 176m away as Gerald figures above, then a 42 cm shift in baseline (0.13°) is the difference between seeing and not seeing. The sun for its part moves 0.13° in about 45 seconds. So then what are the odds that the thing would be seen twice on different sols from different positions? Pretty low right? Therefore by Ockham's Razor it's not a reflection.

Is there any chance to do time lapse photography of the area in question? Zooming in to the area with 64X64 or 256X256 pixel coverage should not overburden the uplink bandwidth I would think
and a resultant "movie" with ~ 1 sec intervals should catch any reflections. Also doing this at night would be interesting.

I have wished for a meteor watch movie at night but don't know if the rover has this capability or not. In October it would be really interesting to see if a meteor storm happens.

[djellison]

should not overburden the uplink bandwidth I would think

Bandwidth is rarely a constraint on activities such as this. Time available in the rovers schedule as well as power is the limit. Consider - while the rover is doing this, it can't be driving / doing other remote sensing / using the arm etc etc. Moreover, the mast can not be pointed sunward for extended periods - there are rules that constrain the duration of sun-pointed activity to avoid damaging ChemCam's optics.