Is it likely that scientist can live outside of earth for
along period of time, with only sustaining themselves wtih
oxygenfrom plants in which they carried with them to the
outerjourney?

It is likely that scientist can live outside the earth but not for a long time. They can sustain themselves with oxygen from plant, but not for long. The planet outside the earth is harsh, and not favourable to human and plant. The only way they can survive is to grow the plants In a controlled environment.

Explanation:

how to make a simple air condition

the density(ratio between mass and volume as m/v) decreases from top to bottom in periodic table group as the size increases and nuclear charge decreases. but in periods density increases from left to right as atom size decreases and nuclear charge increases.