I think this is going to be an endless discussion. The flat earth believers are going to say it is a squirrel/rodent. The round earth defenders are saying it is a rock.
The flat earth believer point of view:
NASA is lying about its achievements and fakes landings, by taking photos on Earth and present them as photos from Mars.
The photo is evidence of a squirrel, which confirms the assumption NASA is lying.
To me this is circular thinking, because you already have a biased view when looking at this photo. NASA is lying > We spot a squirrel > therefore NASA lying is confirmed
To me there is no reason to assume they are lying in the first place. For numerous reasons. First off is because everything they do is monitored by thousands of people. All sorts of things are publicly available, including live footage from spacewalks. Second, we can check the ISS is in orbit from Earth. We make use of technology which uses satellites, think of GPS. A conspiracy on the level the flat earth believers think this should be, is impossible as it involves thousands, if not millions of people.
We already know the NSA, who workes with only a "handful" of people and in top secrecy, also had a leak, because of one individual. Even that top secret organization could not prevent information from spreading.
Perhaps there are people out there who think even that is a set-up to trick us into thinking in a particular way. To those, perhaps your whole life is a lie. Maybe you're just an imagination in someone else's mind.
To me the object on the photo does not look like a squirrel. It would be a very strange squirrel if you ask me.
And I am not even looking for it to be something else than a squirrel. If it would be a squirrel, I would accept is to be true.
However, we know from tens of other photos things not always appear what they really are. It is in our nature to quickly look for recognizable things. It is our instict to look for danger. Better safe then sorry. If it would have been a predator, you better get the hell out of a there. For all you know, you may be next on the menu. Run and survive. If it is a rock, you do not have to run for it. However, if it looks like a predator but it is a rock....well you ran for nothing, but at least you were safe. If it looks like a rock, but it is a predator...well you walk straight into danger.
That is why you recognize patterns in pretty much anything. Better safe then sorry.