In 2038, I witnessed the final moments of the Earth with my own eyes. (The word "moment" is actually misleading. I wasn't looking at it through an astronomical telescope, but through a monitor I was looking at images sent from a space station orbiting the Earth. There was a time lag of 3 minutes at the earliest and 21 minutes at the latest for images from the space station to reach Mars.)
Fireballs bloomed one after another all over the earth. The red was a vivid red similar to Chinese hibiscus, and as it spread, it gradually lost its color and turned white. I fell in love with its beauty. Partly because there is no sound. In fact, under that pure white cloud, all the people on earth must have been screaming. Thinking about it made my heart hurt.
The fireball was actually a nuclear weapon. A nuclear weapon is a weapon that utilizes the nuclear fission reaction or nuclear fusion reaction of atoms. You may think that it is not a big deal because it is caused by minute atoms, but it causes enormous damage that is incomparable with the air strikes and poison gas used in World War I. Specifically, a single nuclear bomb the size of a truck bed can destroy an entire city and kill or wound tens of thousands of people in an instant. China and the United States started a war using nuclear weapons, and the earth was destroyed.
I will not write here the complicated circumstances leading up to the war. Because it's not about your world. Our twenty-first century is not the future of your world. Each world has a different history. (To give a specific example, your world's America did not participate in World War I, but my world's America went out and suffered many casualties.)
There may have been people still alive on Earth. Perhaps they were in the bunker. However, the surface became uninhabitable for any creature, let alone humans.
On the other hand, we were stranded on Mars, without a place to return to, no one to pick us up, and helpless. There were government officials and military personnel at the Mars base. But they did not impose their party and military rules on us scientists and engineers. they were afraid of us. They subconsciously knew that we would not comply, even if they threatened us with weapons. (Actually, just before the nuclear war, a Chinese government official asked us to evacuate from Earth to Mars. We told them it was difficult because we didn't have time. But the soldiers threatened us with guns, and we had no choice but to do it. As a result, Chinese government officials have been transported to a place neither on Earth nor on Mars, perhaps somewhere in the universe where humans cannot survive. They think we did it on purpose, although it was caused by a miscalculation caused by being rushed. ). That is why they have entrusted us scientists with full power.
The first thing we did was rescue the space station crew in Earth orbit. The Mars base has enough facilities to be semi-permanently self-sufficient. Vegetables were also grown, and it is possible to expand the residential area. Once that was done, we sought cooperation from our rival US bases.