<p>The image in question appears to come down from the rover &quot;down-look&quot; camera.  <a href="https://mars.nasa.gov/mars2020/multimedia/raw-images/EDE_0004_0667288889_516ECM_N0010052EDLC00004_0010LUJ01" rel="nofollow noreferrer">Here is a raw image of that</a>, while <a href="https://mars.nasa.gov/mars2020/multimedia/raw-images/EDE_0004_0667287989_518ECM_N0010052EDLC00004_0020LUJ01" rel="nofollow noreferrer">this is a raw image taken next to it</a> (you can line up the crater part in the left of the first with the main crater in the second).</p>
<p>While both list Sol 4 as the acquisition date, they list Feb. 23 and Feb. 24 as the Earth dates, while local time is separated by just 14–15 minutes.  Despite those dates, which seem pretty incompatible to me, I have a feeling that that's when the images were downlinked to Earth from the rover.  The &quot;down-look&quot; camera <a href="https://mars.nasa.gov/mars2020/spacecraft/rover/cameras/#Descent-Imaging-Cameras" rel="nofollow noreferrer">is &quot;mounted beneath the rover, looking downward at the surface during landing.&quot;</a>  And, those do not look like images of the surface to me that I would expect if you were just a few inches away, instead they look like meter-scale pixels, not millimeter-scale pixels.  So, I think these were images taken while it was landing, a few minutes apart.</p>
<p>Given that premise, I looked at <a href="https://mars.nasa.gov/resources/25630/perseverance-and-mars-2020-spacecraft-components-on-the-surface/" rel="nofollow noreferrer">a close-up of the HiRISE image of the landing site, which is nominally 25 cm/pix</a>, and that crater in the second image matches the crater in the HiRISE image on the left, just rotated about 90° clockwise.  So, this was a descent image, not an image from the surface.</p>
<p>With that knowledge, those are sand ripples, which are basically small dunes.  These are all over Mars, so it's nothing unusual and does not have anything to do with it being near or in a lakebed, but just have to do with the wind and particle size of the martian regolith.</p>

CC BY-SA 4.0
2021-02-28T20:23:04.743Z
Thanks, I thought about this opportunity also, seems it's simplest explanation indeed.
Agnius Vasiliauskas
CC BY-SA 4.0
2021-02-28T20:11:30.340Z
2021-02-28T20:11:30.340Z
Stuart Robbins
<p>Good to know that perseverance rover has touched the surface of Mars finally. We will have nice new opportunity window for exploring our closest &quot;friendly&quot; planet of solar system.
Here's one of Mars photos perseverance has made :</p>
<p><a href="https://i.sstatic.net/4KWEP.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/4KWEP.jpg" alt="enter image description here" /></a></p>
<p>Question is, What are this object roots marked with rose color ? I suspect it can be remains of past river in Mars or is it just an artifact of wind+sierra effect ?</p>

CC BY-SA 4.0
2021-02-28T12:21:55.983Z
They look like they are at the top of an escarpment, and so could be caused by material falling down the slope,  crater rims often have such ridges at their edge, but this escarpment might be alluvial.
James K
CC BY-SA 4.0
2021-02-28T12:47:31.460Z
Yeah, I also think more about alluvial case, because it can be seen in picture that this sediments network is **highly periodic** (grate-like structure). This happens when some constant force (like water) is pushing forward various sediments on the floor.
Agnius Vasiliauskas
CC BY-SA 4.0
2021-02-28T12:50:38.650Z
But if my reading of the topography is right, this is at the top of a cliff, and water doesn't usually run along the top of an escarpment.
James K
CC BY-SA 4.0
2021-02-28T12:55:27.013Z
Hm.., I'm not the expert of topography. Can you please expand your knowledge in topography that this structure is really located at top of a cliff ? Btw, there are some cases of water running on top of cliffs,- see waterfalls.
Agnius Vasiliauskas
CC BY-SA 4.0
2021-02-28T13:34:00.670Z
I'm not either, I'm just looking at the shadows
James K
CC BY-SA 4.0
2021-02-28T13:49:53.180Z
Shadow dropping on this structure can also mean that it is located at foothills.
Agnius Vasiliauskas
CC BY-SA 4.0
2021-02-28T15:29:57.620Z
This might belong on Space SE...
WarpPrime
CC BY-SA 4.0
2021-02-28T17:06:42.927Z
I agree with @JamesK - This looks more like an escarpment than a river. However, what you didn't outline, to the right of what you did outline, might well be a former river.
David Hammen
CC BY-SA 4.0
2021-02-28T19:35:58.703Z
@DavidHammen Can you please express this as an answer of yours with outlining your mentioned former river in that pic? Thanks.
Agnius Vasiliauskas
CC BY-SA 4.0
2021-02-28T19:55:07.530Z
@AgniusVasiliauskas Can you provide a link to that image?  It looks like an orbital image from another craft, or something from the Perseverance descent, because those look like sand ripples, not anything else, to me.  I also don't see that image in the public galleries, but maybe I'm not looking in the right place.
Stuart Robbins
CC BY-SA 4.0
2021-02-28T20:00:06.290Z
Okay, I found the image, at least a greyscale one.  It's from the down-look camera and I'll write an answer about it.  I think the site I'm looking at that's listing "acquired" date/time is saying when it was beamed back to Earth, for there's no way that it is getting that kind of image while looking down at the surface when it's on the surface.
Stuart Robbins
<solar-system><mars><planetary-formation>
River-like artifact in perseverance rover's photo of Mars
Agnius Vasiliauskas
# River-like artifact in perseverance rover's photo of Mars

(Asked by: username_0 on 2021-02-28)

Good to know that perseverance rover has touched the surface of Mars finally. We will have nice new opportunity window for exploring our closest "friendly" planet of solar system.
Here's one of Mars photos perseverance has made :

[![enter image description here](https://i.sstatic.net/4KWEP.jpg)](https://i.sstatic.net/4KWEP.jpg)

Question is, What are this object roots marked with rose color ? I suspect it can be remains of past river in Mars or is it just an artifact of wind+sierra effect ?

**Tags:** solar-system, mars, planetary-formation
> **Comments:**
> **username_1**: They look like they are at the top of an escarpment, and so could be caused by material falling down the slope,  crater rims often have such ridges at their edge, but this escarpment might be alluvial.  
> **username_0**: Yeah, I also think more about alluvial case, because it can be seen in picture that this sediments network is **highly periodic** (grate-like structure). This happens when some constant force (like water) is pushing forward various sediments on the floor.  
> **username_1**: But if my reading of the topography is right, this is at the top of a cliff, and water doesn't usually run along the top of an escarpment.  
> **username_0**: Hm.., I'm not the expert of topography. Can you please expand your knowledge in topography that this structure is really located at top of a cliff ? Btw, there are some cases of water running on top of cliffs,- see waterfalls.  
> **username_1**: I'm not either, I'm just looking at the shadows  
> **username_0**: Shadow dropping on this structure can also mean that it is located at foothills.  
> **username_2**: This might belong on Space SE...  
> **username_3**: I agree with @JamesK - This looks more like an escarpment than a river. However, what you didn't outline, to the right of what you did outline, might well be a former river.  
> **username_0**: @DavidHammen Can you please express this as an answer of yours with outlining your mentioned former river in that pic? Thanks.  
> **username_4**: @AgniusVasiliauskas Can you provide a link to that image?  It looks like an orbital image from another craft, or something from the Perseverance descent, because those look like sand ripples, not anything else, to me.  I also don't see that image in the public galleries, but maybe I'm not looking in the right place.  
> **username_4**: Okay, I found the image, at least a greyscale one.  It's from the down-look camera and I'll write an answer about it.  I think the site I'm looking at that's listing "acquired" date/time is saying when it was beamed back to Earth, for there's no way that it is getting that kind of image while looking down at the surface when it's on the surface.  

---

## 1 answers

### Answer by username_4 on 2021-02-28. Score: 2 | Accepted answer

The image in question appears to come down from the rover "down-look" camera. [Here is a raw image of that](https://mars.nasa.gov/mars2020/multimedia/raw-images/EDE_0004_0667288889_516ECM_N0010052EDLC00004_0010LUJ01), while [this is a raw image taken next to it](https://mars.nasa.gov/mars2020/multimedia/raw-images/EDE_0004_0667287989_518ECM_N0010052EDLC00004_0020LUJ01) (you can line up the crater part in the left of the first with the main crater in the second).

While both list Sol 4 as the acquisition date, they list Feb. 23 and Feb. 24 as the Earth dates, while local time is separated by just 14–15 minutes. Despite those dates, which seem pretty incompatible to me, I have a feeling that that's when the images were downlinked to Earth from the rover. The "down-look" camera [is "mounted beneath the rover, looking downward at the surface during landing."](https://mars.nasa.gov/mars2020/spacecraft/rover/cameras/#Descent-Imaging-Cameras) And, those do not look like images of the surface to me that I would expect if you were just a few inches away, instead they look like meter-scale pixels, not millimeter-scale pixels. So, I think these were images taken while it was landing, a few minutes apart.

Given that premise, I looked at [a close-up of the HiRISE image of the landing site, which is nominally 25 cm/pix](https://mars.nasa.gov/resources/25630/perseverance-and-mars-2020-spacecraft-components-on-the-surface/), and that crater in the second image matches the crater in the HiRISE image on the left, just rotated about 90° clockwise. So, this was a descent image, not an image from the surface.

With that knowledge, those are sand ripples, which are basically small dunes. These are all over Mars, so it's nothing unusual and does not have anything to do with it being near or in a lakebed, but just have to do with the wind and particle size of the martian regolith.

> **Comments:**
> **username_0**: Thanks, I thought about this opportunity also, seems it's simplest explanation indeed.  

---

