@twofish-quant -
"Carbon planets" have been proposed as a possibility for stellar systems that form in carbon dominated molecular clouds. Some stars are carbon rich, and some interstellar clouds have enough carbon to absorb all of the Oxygen in CO and allow for the existence of substantial...
I would vote for Venus. Put a Sunshade at the Sun-Venus L1 Lagrange Point (about 100 kilotons of metal should do), and cool the surface down to something reasonable. Once that happens, turn the Sun partially back on and introduce biology (plants) to turn Carbon Dioxide into surface material...
The atmosphere of Venus is almost entirely CO2, but Venus is (from spacecraft observations) compositionally very similar to the Earth, including its Carbon abundance. The crust + atmosphere of Venus contains almost the same amount of Carbon as does the crust + oceans + atmosphere of the Earth...
Let's say I had two clocks that were synchronized on Earth. Ignoring the effects of traveling to Mars I take one clock and put it on Mars.
Now what happens to the clock on Mars? And why?
The Martian clock will tick faster, and thus gain on the terrestrial clock, and so they will get out of...
Clocks tick faster on Mars. Its gravity is less, and (more importantly) it is further out in the solar gravitational well. Just as GPS clocks are made to run fast to match UTC, MTC clocks could be made to run fast and not drift off from UTC, but (unlike GPS) the eccentricity of the two orbits...
Time is slippery, and this question has at least 3 (really 4!) answers.
First, there is "what day is it?" Mars has a different length of day than the Earth's - close, but not the same. A Mars day is called a "sol;" lander activities being measured in sols. For some reason I cannot fathom...