I think the author was trying to say "I mean, look, Earth and Mars are not that different, and even though we don't have any current evidence for the appropriate chemical conditions on Mars, I don't see why it couldn't have been where life started instead of Earth, because ... well, just because they're sort of similar, kind of. Oh, and next to each other."
There's plenty of evidence Mars once had much more surface water than it does today. IIRC liquid water is one of the primary preconditions for the evolution of Earth-like life.
What about Mars disfavoured it?
In two hundred years, conclusions drawn from what we currently know will be as out of date as conclusions from two hundred years ago are today. Or to put it another way, things known to the best of our knowledge are both as good as we can do and probably wrong because one of the things we know is that historically most of what people know at any given time turns out to be wrong at any given time.
I'm entirely down for our descendants in 200 years laughing at our scientific parochiality, just like we often get to do at our double-century antecedents. But that doesn't justify writing right now that Mars and Earth have a priori likelihoods of being the origin of life in the solar system.
Yes, leaving aside the 20% lower luminosity of the sun[1] a few billion years ago (when Mars had a reasonable atmosphere) putting Mars outside the habitable zone, and Mars's lack of plate tectonics and a protective magnetic field: -
Life certainly could have evolved on Mars. I expect that one day prion-like or viroid-ish molecules may well be found. But so what?
It's one or two billion years from there to a bacterium, let alone a lost civilisation. And Mars did not have the time.
But it would seem to need them for sustained evolution to be possible. So as I said, I'd expect lifeforms at the complexity level of viroids, but not at the level of eukaryotes.
Evolution needs time, lots of time in which conditions don't change too much. (Chemistry that works in dilute solution at 300K doesn't work well at 200K or 500K.) It also needs populations to be able to spread to new areas.
Without a magnetic field, Mars's atmosphere got stripped off. No more liquid water, no more areographical distribution, so no more evolution.
Plate tectonics is needed to ensure that nutrient chemicals don't get locked up permanently in sedimentary rock.
As for the habitable zone, life as we know it needs liquid water on the surface. Mars may have briefly been habitable, but not for long enough.
To be a challenge, the article needs to provide plausible alternative evolutionary pathways that get us eukaryotes without needing these things (time, liquid water, chemical recirculation, limited variability in physcal conditions). It doesn't do that. It's just spitballing.
If early Mars was OK for life to begin, then so was early Earth. We don't need any interplanetary travel.
https://www.nasa.gov/press-release/nasa-confirms-evidence-th...
Yes, life could have 'theoretically' started anywhere where life by definition is possible. Fine, but that's a tautology, and in contrast to what the author seems to believe actually not scientific and thus deserves to be rejected.
If we're talking about scientific statements then show me life actually existing somewhere that isn't earth and then we can make some grounded theories
I mean when you say theoretically and then make a big not necessarily obvious statement you should actually point out which theory you're using.
What the author is saying is "theoretically, life could have started on Mars just as easily as it did here".