” Supplying fuel for a Mars expedition from the lunar surface is often suggested, but it’s hard to make it pay off – Moon bases are expensive, and just buying more rockets to launch fuel from Earth is relatively cheap. “
” The communications delays between Earth and Mars can be half an hour or more, so the people on the ground can’t participate minute by minute in Mars surface activities. “
” Liquid oxygen is one of the cheapest manufactured substances on Earth. In large quantities, it costs pennies per kilogram – cheaper than milk or beer. “
” The original specifications for Apollo navigation called for the ability to fly a complete mission, including a lunar landing, with no help from Earth – none, not even voice communications. “
” Speaking of photography, while the Apollo 8 crew shot hundreds of photos, there was one that got everybody’s attention: a blue-and-white Earth rising over a gray moonscape. “
All 5 Henry Spencer Quotes about Earth in picture
Topics: Earth quotes