Mars: Crater or hill? Innie or outie?

This is a recent image from Mars Reconnaissance Orbiter.

First I'd like to just post it as is. Without context.
It's really hard to tell if this is a crater, or a small hill.
It's almost perfectly round, so my first thought is crater.

But look closely, and tell us what you think.
I'll post the original context image a bit later.

It looks like an innie to me, but it's hard to tell without being able to tilt the image or without any other topographical features to establish reference points.
Looking straight down with only 2 dimensions makes it difficult, but I don't see the normally craggy edge seen on most craters, and I don't see any ejecta.
If it is an innie it would be very old and eroded.

Could you post the name of the feature so I can look it up on World Wind.


[edit on 19/2/2007 by anxietydisorder]

When I first saw it. I thought it was an outie, but after starring at it for a while, it turned into an innie. But I think it is a hill.

Looks like an 'outie' with a shallow 'innie' , in the center.

Almost like an ancient volcano.

Notice light source from high,and left, and leaving shadow on right side, would beg an elevation rise on outer ring , no?

Also strange there seems to be No shadow in the center ring. Almost like it's a plateau .

And X marks the spot. What's That all about? Curious.

Looks like an "outie"

There are some optical illusions on the net similar to this.

I forget what they call this sort of thing though.

It all has to do with where you perceive the light source to be.

But as with the optical illusions, it may appear either way, or appear to change while looking at it, depending on where you focus your eyes.

It could even be a cleverly shaded and lightened "flat" surface. Think of a painting for instance, with emphasis on depth perception.

I'm curious to find out the true context. Which direction is the light source coming from.

I'll bet it is actually a crater. lol

[edit on 2/19/2007 by Mechanic 32]

Where does the light source come from when the picture was taken?

If the light source is coming from the left side of the image it would be a hill.
If the light is coming from the right side of the picture it would be a crater.


Throw us a bone spacedoubt, give us a bit more information about the image.

I think it is pretty clear the light source is from the left.

Look at the smaller debris, for confirmation. All the shadows are on the right, no?

Well, I don't want it to drag on for too long.
SO here is a small original.

Puts things in perspective.

How about now, innie or outie?
It's near the lower left of the image.




[edit on 19-2-2007 by spacedoubt]

Now it looks like an outie.

I'm going to look at Utopia Planetia with World Wind and try to find other images of this.


EDIT:

Observation Geometry
Image PSP_001503_2180 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on 21-Nov-2006. The complete image is centered at 37.5 degrees latitude, 82.8 degrees East longitude. The range to the target site was 293.5 km (183.5 miles). At this distance the image scale is 29.4 cm/pixel (with 1 x 1 binning) so objects ~88 cm across are resolved. The image shown here has been map-projected to 25 cm/pixel and north is up. The image was taken at a local Mars time of 03:23 PM and the scene is illuminated from the west with a solar incidence angle of 49 degrees, thus the sun was about 41 degrees above the horizon. At a solar longitude of 138.8 degrees, the season on Mars is Northern Summer.
hiroc.lpl.arizona.edu...

[edit on 19/2/2007 by anxietydisorder]

I vote "outie". There's a couple more similar structures in the area but not such perfect circles.

I tried to find topographical data for the area but can't get anything down to the scale of the image that spacedoubt posted.

This image is a false color topo shot of the area from the Mars Orbiter Laser Altimeter, but the resolution sucks when you zoom in.



Just to give everyone an idea of the scale, the crater is 60 Km across, and the mound in the original image is so small that it can't be seen in this data set.

For reference, and as far as I can tell, the feature would be at the south east edge of the crater, and out about 5 Km.
I think it would be safe to assume that it was originally ejected from the crater when the impact occurred, and over time, the winds have worn it down to the feature we see today.



EDIT: screwed up east and west




[edit on 19/2/2007 by anxietydisorder]

the shadows on the upper right seem to indicate an upward slope from that direction, but if it is depressed in the center shouldnt the upper right of the INNER quadrant be lighter shade?
i vote outie with a domed roof?????

Thanks for the research AD.

Seems like the feature is just a few meters across.

It's interesting that a positive relief feature could be so round though.
Thats what made me go hmm..and yes there are other similar humps in the same image..



Then, of course, there is the feature in the center, that appears to be flipping us the bird.

looks like an outie to me with a flat top and the light and shadows seem to indicate that to me. though i am no picture expert.

Originally posted by spacedoubt
Then, of course, there is the feature in the center, that appears to be flipping us the bird.

It's a bomb!

I'm goin with Martian wart. The erosion patterns around the perimeter.

This is fun. When are you going to post the next one, spacedoubt?

Mechanic..
Yeah, that is kinda fun.
I'll post some more stuff, when I get the time to download and peruse those giant image files..

In the meantime..any theories on how a perfectly circular hill might be formed?
I'm still pretty curious.

One theory? How about three or four different theories.

1. How about that it is actually a round and somewhat flat object, once covered by a fine sand that may or may not have solidified through the eons.


2. Underground pressure buildup? Not enough to break the surface material, just enough to push it upward.

3. a "Splat" of hot magma, then solidified? (kind of like if you drop a small drop of liquid on a flat surface. It leaves a round raised puddle)

4. It is a buried flyng saucer.

Well, in all fairness it doesn't really look "perfectly" circular. Close though. I'm in agreement with AD though in that it's probably something spat out of an impact that went *plop* back onto the surface. Could have been launched high enough to form a teardrop shape while coming back almost straight down.

However it could be a very very old volcano. The surrounding terrain resembles seabeds of Earth, so the volcano originally being underwater could explain the lack of significant features, beyond the flat top.