In recent days I have been asked several times why the atmosphere on Mars left. Mars in on peoples mind and that includes wondering ‘why it’s not the same as Earth and yet in many ways it is or was’. It is important to note that Earth & Venus were alike once too! In fact one of the planets went far to the left & the other, to the right.
Venus & Mars both started out like us but each changed. If one were to be looking at Climate Change then this is worth taking note of. Both planets hold invaluable information regarding Climate Change.
In the case of Venus, the atmosphere is much thicker than that of Earth. There is still data to be gleaned/learned from the current temperature structure and how Venus actually became the lava planet of present from its former status. Climate scientists believe that due to runaway greenhouse gases that occurred as a result of the Sun gradually increasing its strength. Eventually all of the water on Venus evaporated and entered the atmosphere. Water Vapor is actually a powerful greenhouse gas. Once in the atmosphere it then assists in heating the planet more which in turn causes more water to evaporate…more water then heats the planet…it’s a vicious cycle.
Mars had a somewhat different journey. The timing for both actions would seem to be similar; although the actions differ they both reacted to changes in the Sun in its youth. Back about 4 billion years ago (+/-) the Sun’s ultraviolet light was more powerful. The solar wind –charged with particles of the Sun, was a major facilitator in the loss of atmosphere from Mars, and it still is today. Thanks to MAVEN (MAVEN is the ‘Mars Atmosphere and Volatile Evolution’, the first spacecraft dedicated to exploring the upper atmosphere of Mars) we have learned much including that long ago solar eruptions played a huge role in stripping away the planet’s atmosphere. A lot of that action is thought to have taken place 4.2 to 3.7 billion years ago.
Today we know Mars as a cold and dry place (albeit with scattered areas of seasonal water flow), but things were very different once - the Red Planet was relatively warm billions of years ago, with extensive lake-and-stream systems and possibly a large ocean that covered much of the Martian surface.
So, put simply; the window for life to take root across broad stretches of the Martian surface may have closed shortly after the first microbes evolved on Earth. Does that mean the life created (if it was created) didn’t change and adjust? No. Considering that, I would search for life it the underground caverns (cathedrals really) – the lava tunnels.
As for life on Venus? I’m not counting it out, but I wouldn’t begin to know where to look and what to look for!
A SIDE NOTE – ON MARS THERE ARE AURORAS SIMILAR TO OUR NORTHERN LIGHTS.