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Earth Mars Space Science

Curiosity's Latest High-Res Photo Looks Like Earth 215 215

New submitter bbianca127 writes "Curiosity sent a picture down to us, and it looks a lot like Earth. Actually, the picture's color quality has been changed — to human eyes, the landscape would look a lot more reddish. Still, it looks remarkably like the southwestern United States (bringing to mind the Arrested Development quote about how Lucille Bluth would rather be dead in California than alive in Arizona)." Definitely a different sense of the place than the one given by the reddish-brown posters I remember from elementary school.
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Curiosity's Latest High-Res Photo Looks Like Earth

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  • by Kenja (541830) on Thursday August 16, 2012 @11:43AM (#41011925)
    They use black & white (greyscale) cameras because you can get higher resolution for the size & weight. They then take three photos with different filters to simulate color.
  • Both versions (Score:5, Informative)

    by neoshroom (324937) on Thursday August 16, 2012 @11:46AM (#41011955)
    Here is a page on the MSL's site where you can see both versions of the photo: []

    One is white-balanced and one colored. The white-balanced version represents what the scene would look like to human eyes under an Earth sky. The colored represents what the scene would look like to human eyes on Mars.

    The point of using white-balanced photos is that geologists are used to looking at rocks on Earth. So when a geologist wants to judge rock characteristics using color, it helps to white-balance it so the color is similar to what it would be if looking at those rocks on Earth.

  • Re:White-balanced (Score:5, Informative)

    by need4mospd (1146215) on Thursday August 16, 2012 @11:51AM (#41012045)
  • Re:third parties? (Score:5, Informative)

    by Anonymous Coward on Thursday August 16, 2012 @11:52AM (#41012063)

    Because NASA doesn't have advertising?

    (Which is a completely wasted opportunity.)

  • Re:Truth (Score:5, Informative)

    by kubernet3s (1954672) on Thursday August 16, 2012 @11:58AM (#41012139)
    Yyyyeah...they're not "altering" the photo. What they're doing is balancing the color so that people can know what they are seeing. The reason for this is that the Martian atmosphere has radically different color properties from that of our own. What this means is that visible observations cannot be made reliably: for example, a red rock on mars may not actually be red as we understand the color, and so conclusions geoloists make based on a color may be erroneous, because they are basing those conclusions on colors observed under earth's sky.

    If anyone's interested, another scene is shown with and without white balance here: []
  • Re:White-balanced (Score:5, Informative)

    by Sarten-X (1102295) on Thursday August 16, 2012 @11:58AM (#41012147) Homepage

    As much as I love the awesome idea of moving a chunk of terrain between planets, I'm going to shoot for an informative mod and answer the question.

    There is a sundial mounted on Curiosity [], with a few colored stripes on it. Those stripes' colors (red, green, blue, and yellow) were recorded under Earth's lighting, Now that those same stripes are on Mars, their apparent color change in new pictures is the result of Mars' different lighting. By comparing the stripes' pictures, an approprite transformation can be determined, then applied to other pictures to compensate for the change in lighting.

    We are sure because we're assuming that those stripes' actual colors haven't changed significantly during flight or landing.

  • by fuzzyfuzzyfungus (1223518) on Thursday August 16, 2012 @12:01PM (#41012189) Journal

    Not really...

    If you don't mind being unable to take color shots of relatively fast moving things, you can use a conventional greyscale sensor, swap color filters between frames, and then crunch the result into a color image(or, if you have the space and don't mind a moderately complex optics package, you can have three greyscale sensors, each with a fixed color filter). If you need a color image within one frame, you use a fixed bayer(or similar) filter and demosaicing. Eats nontrivial resolution compared to the pure greyscale or swapped filters strategy; but you get everything in one shot and fewer moving parts. Then you have the somewhat oddball Foveon approach, where your greyscale sensors are stacked vertically, and use the different rates of absorption in silicon of different frequencies to do the filtering...

    In very broad terms, they all have the 'greyscale sensors and filters' strategy; but there are a fair few ways to go about it. If you count chemical and biological sensors, you are more likely to find sensor elements that are actually tuned to a specific wavelength, rather than filtered to it; but the final image is still a matter of crunching together results from individual elements that are really only giving you intensity data for a relatively narrow slice of frequencies.

  • Re:White-balanced (Score:5, Informative)

    by necro81 (917438) on Thursday August 16, 2012 @12:19PM (#41012441) Journal
    On the rover are color calibration targets (here is the one for the rover's arm's instruments []). We know exactly what the colors of those targets are supposed to look like, when imaged by the cameras on the rover, under normal Earth-like lighting conditions. By looking at how those targets appear in the images we get back under Mars lighting conditions, we can do two things:

    1) Learn a lot about the lighting conditions on Mars.
    2) Correct the appearance of images we get back to correct for that Mars lighting.
  • Re:Mind blown! (Score:5, Informative)

    by nashv (1479253) on Thursday August 16, 2012 @12:36PM (#41012701) Homepage

    Obviously this must mean that Martian rocks and Earth rocks share a common ancestor!

    Yes. It does. That common ancestor is called the protoplanetary disc [] which led to the formation of the inner solar system.

    Now go troll somewhere else.

  • Re:Great summary (Score:0, Informative)

    by Anonymous Coward on Thursday August 16, 2012 @12:36PM (#41012717)

    You're using the phrase "begs the question" incorrectly.

  • by Jeremy Erwin (2054) on Thursday August 16, 2012 @12:37PM (#41012731) Journal

    New Mexico, to be precise [], near Albuquerque.

  • Re:White-balanced (Score:5, Informative)

    by Joce640k (829181) on Thursday August 16, 2012 @12:39PM (#41012747) Homepage

    Gee, I wonder if such an image could be available on NASA's web site. Nah, that's unthinkable.

    Oh, wait, here it is: []

  • Re:White-balanced (Score:5, Informative)

    by holmstar (1388267) on Thursday August 16, 2012 @12:55PM (#41012963)
    You would, but geologists wouldn't. They are used to what rocks and minerals look like under our own earthly lighting. As such it makes sense to adjust the color of the image to match earth-normal lighting conditions.
  • Re:Great summary (Score:5, Informative)

    by h4rr4r (612664) on Thursday August 16, 2012 @01:01PM (#41013043)

    Begs the question is more properly used when I say "So now that you stopped beating your wife, how is your marriage?" That begs the question of if you ever beat your wife at all.

    The poster asking about a robot and a mirror should have used "Raises the question" instead.

  • Re:White-balanced (Score:5, Informative)

    by HapSlappy_2222 (1089149) on Thursday August 16, 2012 @01:44PM (#41013619)
    Even on earth we have this issue (I've made a fairly healthy living navigating through color space to color space and light source to light source over the years). People seem to forget that our own sunlight can vary during the day, geographical location, cloudy days, etc, and indoor lighting is the beast with a billion backs. Even your own eyes can betray you, needing a moment to adjust, and often one eye sees color slightly differently from the other.

    Color scientists have had an absolute color and light source standard to measure against (CIE LAB) or 40+ years; Mars (or anywhere in the universe that receives light in the visible spectrum) fits just dandy into this model for color transformations, it's just a bit further away than usual. The less light there is to measure, the smaller the total color gamut will be, but you can extrapolate pretty well, if you don't mind some +/- errors along the way.

    Typically, a true simulation would need several hundred color swatches for analysis, plus an iterative scanning approach to nail down the color gamut points that are furthest away (say, blues could be further off than reds, so require more attention for a transform). Still, for a general "this is approximately how it'd look on Earth" a 4 swatch RGBY spectrum is close enough.

    It's something like the difference of having a precision of tenths to a precision of hundred-thousandths, when all you're doing is counting apples. You may be plus or minus a tenth of an apple, but so what?

    The only thing that's a little surprising is that they didn't include a calibrated black strip, but I suppose they didn't really need to account for the variation between deep shadow areas or very dark objects in this case.
  • Re:White-balanced (Score:5, Informative)

    by arth1 (260657) on Thursday August 16, 2012 @01:52PM (#41013747) Homepage Journal

    Actually, you probably would see it more like the white balanced photo than the regular one. Your brain is very good at auto white balance.

    Perceptual re-balancing is very different from absolute colorimetric re-balancing, which is what is used here.
    A late evening shot (which this basically is) looks very different when you balance it against a Gretag Macbeth [] card than if you balance it according to human perception.

    NASAs goal here is clearly to make the picture as useful as possible to those who study them, not to give the public a "true" image of what we would perceive if we were there. I think there should be room for both.

  • Re:Truth (Score:4, Informative)

    by element-o.p. (939033) on Thursday August 16, 2012 @01:58PM (#41013867) Homepage
    Not to pick on you, but I'd say that you are perhaps working yourself into a tizzy over nothing. The difference between the photos of Mars from the 70's and what we are getting from the rovers now is hardly the result of NASA "lying...with photoshopped [sic] pictures." It's the result of better technology providing a more accurate representation of what we would actually see if we were there (or in the case of the white-balanced image in TFA, what we would see if that landscape were on earth, which can be useful for certain kinds of scientific investigation).

    There is indeed a very, very fine line between simply processing a digital image and "Photoshopping" a digital image, but I would argue that these images are on the processing side of that line, rather than the "Photoshopped" side of the line. Consider this: my Canon Powershot -- admittedly, a much, much simpler device than Curiosity's cameras, I imagine -- doesn't produce RAW images; it processes every RAW image into a JPG. That introduces aberrations (JPG uses lossy compression after all, among other inaccuracies). Is that an " alteration?"

    Also, a lot of the photos we see from Spirit, Opportunity and now Curiosity are digitally stitched mosaics. For example, if you look at this photo [], you can clearly see the boundaries of many of the individual photos. Are you going to get uptight because this wasn't a single photo, but rather was digitally "altered?"

    If this kind of processing irks you, then I humbly suggest that you take your own digital camera and do some experimentation. Go indoors and shoot a handful of photos at different times of the day, with and without indoor lighting. Do the colors match what you see with your eyes? What if you display the images on a different monitor? If you have the ability to shoot photos in RAW and JPG formats, compare them both with what you see. Now play with some of the settings on your camera. My Powershot has settings for natural (sunlight) lighting, incandescent lighting, florescent lighting, tungsten lighting, etc. These software filters adjust the white balance to the kind of lights that are being used inside your house because the CCD in a camera doesn't react to all frequencies of light in the same way your eye does. In fact, most digital cameras include an IR-cut filter over the CCD because the CCD is much more sensitive to IR light than your eyes. Is that hardware filter "altering" the photo? Your eye won't detect those frequencies of light, but it's really there, and the filter is removing it from the photo.
  • by Max Threshold (540114) on Thursday August 16, 2012 @02:00PM (#41013903)
    When the spectrum of ambient light does not match that of "white" light (which is simply the particular spectrum we evolved to perceive), the eye's photoreceptors become disproportionately fatigued, and perception of the light's color drifts toward white. You can experience this phenomenon yourself if you light a room entirely with red party lights. Soon, your red photoreceptors will become fatigued and the colors of objects in the room begin to appear more normal. I think explorers on Mars would experience the same effect. So photos like this are actually how it would look to them.
  • by Jappus (1177563) on Thursday August 16, 2012 @02:33PM (#41014361)

    The atmosphere is so thin it's basically vacuum, so the view of the stars should be pretty good. If we could engineer cottonwood trees that thrive in vacuum, high radiation, temperatures as low as -150 celcius, and no water, we'd be good there too. Of course then we'd have to engineer humans that didn't suffer bone decalcification due to the low gravity...

    Snarky as your comment may have been meant, I think you need to check your numbers again what constitutes "so thin it's basically vacuum."

    Mars has an average surface atmospheric pressure of 0.636 kPa. Earth has 101.325 kPa. So yes, while it is 160-times thinner, that's still pretty thick, especially if dust is kicked up. After all, remember that with 1/3rd gravity, much less air friction and no moisture, dust particles can stay afloat for quite some time.

    And then, compare that to the moon, with a pressure of 10^-7 kPa (~1 nPa), Mars still has a 6.36 million times denser atmosphere. And compared to interplanetary space, that's still practically solid, as space has 400.000 times less pressure.

    In other words: If Mars is a near-vacuum at nearly 10^17 times more molecules per cm than interplanetary space, then a snail that moves at only 3*10^10 cm/s.

  • by Intropy (2009018) on Thursday August 16, 2012 @04:54PM (#41016589)

    Areo- is the the Martian equivalent of geo-. It would be areocache.

I never cheated an honest man, only rascals. They wanted something for nothing. I gave them nothing for something. -- Joseph "Yellow Kid" Weil