Misc: What is the heaviest snake?

Questions

antarctica's residents are scientific and ---------- staffs who usually stay no more than a year at a time?

approximately 1/3 of the earth's land surface is----------?

at latitude ---------- degrees south you can sail all the way around the world?

australia is the richest source of mineral ---------- in the world?

because of a large orbital eccentricity, ---------- was closer to the sun than neptune between january 1979 and march 1999?