Mars' lesser gravity (than earth's) is capable only of holding a heavier atmosphere than earth's. That's it. More than 90 percent is carbon dioxide, but since the MSN and today's "theorists" think carbon dioxide is a pollutant, then one could alternatively claim -- theorize -- that the "pollutant" killed off any possible oxygen-producing life forms. Which would also be bunkum.
Simple. Mars is smaller and less massive than earth and therefore does not hold lighter gaseous elements. Its gravity compared to the earth is only about 40 percent.
CO2 is 44.02, while oxygen is "lighter" at 31.99 and nitrogen even lighter at 28.01. So earth holds about 78 percent nitrogen in its atmosphere while Mars simply cannot. Ditto with oxygen.
Trust MSN to print "scientific" theories without basic science behind it. The idiotic article hints that there was an atmosphere similar to earth's which got "eaten away." Loony. Gravity sucks. Less gravity sucks less....
It’s a little more complicated than that. Mars could hold nitrogen. It just didn’t get a significant amount. It can hold oxygen, but the oxygen hooked up with iron, forming a red compound we refer to on Earth as ‘rust’. Hence, Mars is known as the Red Planet.
What Mars can’t hold is hydrogen. It should lose half or more of atmospheric oxygen in roughly 40 million years. If one assumes 4.5 billion years, that’s 112 times to lose half the hydrogen. Thus any hydrogen remaining is buried in ice or subsurface water.
H2O gets broken up by ultraviolet light quickly without lots of ozone in the atmosphere. Gravity on Earth keeps the hydrogen around long enough to recombine with oxygen. Pre-life Earth had no free oxygen. There is no convincing evidence that Mars ever had or has life to date (2022).
Flipside, human engineering could easily bring life to Mars, by adding atmosphere deep enough to hold heat. 1% of the atmosphere of Venus, minus excess sulfur, would work.
Separating the Martian rust into iron and oxygen using standard techniques would help, and then hauling ammonia from any available source to make amino acids/proteins. Glass or clear plastic will block UV. But these changes require human or machine intervention, and won’t happen spontaneously. It takes a Creator to terrform a planet.