Definition: In this task, you will be presented with a passage and have to answer a question based on your understanding of the events inferred from the passage. Try to find the best answer that is most likely to fill in "_". Note that the URLs in the text have been replaced with [Link].
Input: In November 2014, plasma physicist Dr John Brandenburg revealed his theory that an ancient civilisation on Mars was massacred in a nuclear attack. Now, he’s back, and he’s going to be presenting new evidence for his theory at a Nasa-sponsored conference today. He claims there is no other explanation for his proposal that a ‘weapon’s signature’ remains from the attack on Mars. Dr John Brandenburg is to present his theory in Houston, Texas today. He says an ancient Mars civilisation was wiped out by a nuclear bomb. A thin layer of radioactive substances including uranium, thorium (shown in graphic) and radioactive potassium on the surface supposedly provide evidence for this theoryDr John Brandenburg is to present his theory in Houston, Texas todayHe says an ancient Mars civilisation was wiped out by a nuclear bombEvidence for this apparently comes from a 'weapon's signature'And there is apparently no other explanation for his evidenceEarth could also be under threat of attack, claimed Dr Brandenburg 
 Question:He says that the planet once had _-like temperatures and atmospheric pressures, and was abundant with life and an oxygen-rich atmosphere.

Earth