So we've been told Elon Musk wants to take us all to Mars.
Earth's Diameter - 12,742 km
Mars' Diameter - 6,779 km
NBA matches on Mars will be way too easy even for the shortest players. Lord knows what it will do to the Mars colony over many generations.
As far as the Atmosphere on Mars compared to Earth.
Mars' atmosphere is very thin by comparison, with pressure ranging from 0.4 – 0.87 kPa – which is equivalent to about 1% of Earth's at sea level. Earth's atmosphere is also primarily composed of nitrogen (78%) and oxygen (21%) with trace concentrations of water vapor, carbon dioxide, and other gaseous molecules.
The atmosphere of Mars is about 100 times thinner than Earth's, and it is 95% carbon dioxide. Here's a breakdown of its composition, according to a NASA fact sheet: Carbon dioxide: 95.32%. Nitrogen: 2.7%.
However, the surface of Mars is not hospitable to humans or most known life forms due to the radiation, greatly reduced air pressure, and an atmosphere with only 0.1% oxygen.
THEN I'M TOLD
Once again, Earth's Diameter - 12,742 km
The Moon's Diameter - 3,474 km (Basically half the size of Mars)
As far as the Atmosphere on the Moon compared to Earth.
What little atmosphere the Moon has consists of some unusual gases, including sodium and potassium, which are not found in the atmospheres of Earth, Mars, or Venus. ... On Earth, this is considered to be a very good vacuum.
The Apollo 17 mission deployed an instrument called the Lunar Atmospheric Composition Experiment (LACE) on the moon's surface. It detected small amounts of a number of atoms and molecules including helium, argon, and possibly neon, ammonia, methane and carbon dioxide.
As a human, to walk on the Moon unprotected, your death would be fairly horrifying, but probably quick.
Plus, I don't think we've ever been to the Moon, cause if they did, there would be advertising plastered all over it for products like Coca Cola, McDonald's, Apple, Facebook & Google to name but a few.
Now, for any society to exist on either of these two celestial bodies, Billions or Trillions of dollars would need to be spent to make the living area hospitable to humans over as many years possible.
So, if you took all those Billions and Trillions of dollars and created technology to create hospitable living areas and make uninhabited land on this planet new cities then would that make more sense. You don't have to worry about atmospheric issues to start with.
Let's take a look at how much potential unihabited land there is on Planet Earth as of 2018 by a simple Land Mass to Population Scale beginning with a largest countries.
Russia - 17, 075, 200 sq/km
Population - 145 million
Canada - 9, 976, 140 sq/km
Population - 37 million
North America - 9, 629, 091 sq/km
Population - 326 million
China - 9, 596, 960 sq/km
Population - 1.39 BILLION
Brazil - 8,511,965 sq/km
Population - 209 million
Australia - 7, 686, 850 sq/km
Population - 25 million
India - 3,287,590 sq/km
Population - 1.3 BILLION
You can find the other smaller countries and their populations here - https://data.mongabay.com/igapo/world_statistics_by_area.htm
Essentially if the Moon and Mars colonies will be using the Latest and Greatest technology for surviving in those harsh and deadly conditions, why can't we use those same technologies on Earth and reclaim some unused land on this planet to Colonise with Benevolent Intentions both with clean energy and water with advanced technologies like
Ecoloblue
Billions In Change
Keep on shining.