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NASA / JPL-Caltech / Univ. of Arizona
What appears to be a natural bridge spans a channel running through a geological feature on Mars known as Tartarus Colles.
A thin channel on Mars has a naturally occurring bridge over it, as seen in an image from the Mars Reconnaissance Orbiter's High Resolution Imaging Science Experiment camera, or HiRISE. The channel runs through a stretch of knobby terrain called Tartarus Colles.
The origin of the channel itself is unknown, Kelly Kolb from the HiRISE team said in an image advisory, though it was probably not formed by running water as there are no obvious source or deposit regions. "The channel is probably a collapse feature," she wrote.
The bridge itself is "probably a remnant of the original surface," Kolb added. She noted that a depression extending northward from the channel, but not as deep as the majority of the channel, might be in the process of collapsing and enlarging the chasm.
When the image first came to light several years ago, the Planetary Society's Emily Lakdawalla speculated that the channel likely started as a covered lava tube, but that most of the roof has collapsed over time. The remnant left behind bridges the gap. In time, that remnant will most likely fall into the channel as well. That's what happens to natural bridges on Earth.
Bridges also abound on the moon, and you can check them out in 3-D. These features were captured by NASA's Lunar Reconnaissance Orbiter Camera -- and, like the bridge on Mars, were left behind when the surrounding material on the surface fell into a chasm.
Tip o' the log to Universe Today's Nancy Atkinson.
John Roach is a contributing writer for msnbc.com. Connect with the Cosmic Log community by hitting the "like" button on the Cosmic Log Facebook page or following msnbc.com's science editor, Alan Boyle, on Twitter (@b0yle).
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I got an Idea...But bear in mind As Einstein was fond of saying,"if an Idea doesn't sound crazy at first, then its not worth a second thought." Let's remelt Mars solid Iron core. Here's how
http://abrahamsays.blogspot.com/2010/09/forgotten-news-about-lost-city.html
Where are the people asking, "If there's a bridge, who built it?"
the thought has occured to me that astronauts exploring such terrain might find it a bit more unstable than we thought....like the stuck rover, things unexpected can be expected. Really cool pics...I can bet once we got boots on the ground we will get to see this one at eye level. That will really be a great pic. I bet the odds makers are already willing to give odds on various locations for manned mission landing sites.....
Wait!! How come the shadows of all the little pits around there are on the right side of the pit and the shadows on these channels are on the left side? Wouldn't that make this channel really a hill with a pass through it?
Just sayin...
yeah man your right. Those shadows would suggest that the area is not lower but higher. It is not a bridge but a pass-thought. From the direction of the light... if those craters were lower then the shadows would be on the other side from where they are.
Your absolutely correct. Good eye man.
I agree...it looks like the shadows in the craters are on the right side which would suggest that these are bluffs as opposed to ditches. I'm sure they know the position of the sun relative to the camera angle and which way the shadows should be - any insight John?
It's an optical illusion that I saw at first, also. If you look at the mound at the top of the picture, you will see that the light source is coming from the top left corner, so it is two "holes" with a bridge, not two mounds with a pass through.
I think if you were to look at the 3D picture, you would find that the spots to the left and right of the picture are small hills, and the shadows extend to the right. I really have to focus to see it that way in this picture, though.
Another clue is the size and direction of the shadow "north" of the bridge. If the channel "north" of the bridge were an elevated feature, the shadow would be more narrow and would not extend as far "south".
I kept seeing two mesa's with shadows not two holes a a bridge lol
"The channel runs through a stretch of knobby terrain called Tartarus Colles." Those are not craters, they are rock formations.
I think that if we were to see this in 3D, we'd see that the 2 long structures are actually mesas. Since the shadows are to the left, they wouls have to be above the ground and the specks at the upper left and lower right are pits.
Do you not think the HiRise team knows which way the light is coming from in the picture their orbiter took?
You can clearly see the direction of light (from left to right) by the shadows projecting from surrounding outcropping. Given this, the structures in question are clearly channels and not mesas. If they were mesas, the shadow would be on the right of the structure just like all other "protruding" features.
You have it backwards. If they were channels then the shadows would be on the right and into the depressions. Look at he pits on the right side. You can see the shadows inside of them. The long shadows on the left are completely outside, showing them to be above the ground.
It looks like that to me, too. I had to work at seeing it the way it's described in the article; you just pointed out the particulars that caused my eyes to see the "bridge" as a channel.
Both im-in-hell and analogkid have it correct. I work as an imagery analyst and have been doing this job for some years now. The image shown depicts a cleft between two raised ridges or mesas. In comparison to the other minor craters/holes present in the photograph, it is easy to see where the light is emanating from. For the bulk of the image, all the shadows are on the interior lower right hemisphere of the holes. Thus showing there is a light source roughly from the top right. The mesas/ridge have a shadow cast in a downward left angle. This fits with the location of a light source and that they are raised objects. Also, due to the light and shadows you can actually see part of the sidewall for the upper mesa.
There is no bridge. I believe the analyst that handled these needs to return to school.
Enjoy
honestly from the point of imagery analysis, the object shown does not appear to be a bridge but rather a cleft between two raised rock formations/ridges/mesas. Take these factors into account. From other comments, it seems that you do not realize the light is not coming from a direct linear horizontal source to the object. If you take as fact that the light source is from above, you can then factor in angle of shadow per item shown. For the holes/impact craters, if the light source were to the right and behind our equipment, it would match the shadows produced for these portions of the photo. (Raised light source from right side would hit the inner left portion of the bowl but between the elevation of the light source and lip of the bowl, the lower right section would be in shadow.)
For sake of ease of explanation lets say the image is taken in comparison to the sides matching the cardinal points: North South East and West. If you look at the area of the photo with the "bridge", you see what appears to be a bridge at first glance. Now take a look at the northern objective. On the lower right hand side there is an area that is significantly lighter than the rest. Based of the angles displayed, this appears to be the wall of the rock formation. If it were a depression, you would not have the increased light intensity and thus would not have the lighter shading in the photo.
Now for the last portion, the apparant shadows for the "bridge" area. If this were a bridge over a depression or channel, the shadow location would match that of the holes/impanct craters previously mentioned. However, as displayed, the shadows are on the left side. Now if you take into account the probability that the light source is elevated, to the right and slightly north then the shadows projected would match those produced by a light source hitting a raised ridge/rock formation/mesa with a cleft between rather than a bridge over a channel/depression.
The light you see on the right edges of the formation is due to a rounding at the top of the cliff, where the sun's rays would hit it most directly.
Look at the shape of the northern formation, and look at the shape of the shadow. The lower part appears to come to a point and is much more narrow than the upper part. The shadow, though, is larger next to the bottom, and smaller near the top. If the formation was really a raised rock, the shadow given off wouldn't look like that.
Also, look at the smaller marks on the corners of the pictures. They are raised structures, evidenced by the shape of their shadows (especially several on the lower right part). The shadows extend to the right, so they must in the bridge area too.
BG73, you have it exactly right.
No, he does not. Look at an expanded image here: http://hirise.lpl.arizona.edu/PSP_001420_2045
If you click on that first image, it will show an even larger-scale picture. If you can look at those and tell me that the sun's source is on the right, then you need to find a job that isn't imagery analysis.
You know...looking at it again, I do see it with the light coming from the left. Wow, it looks like one of those optical illusions where a 2D object is spinning and you can't tell if its to the left or right. I guess I need to apologize.