The lesson's roughly seven-month Mars trip takes about the same time as its three-day Moon trip.

Which statement correctly compares magnetic protection for the ISS and a Mars-bound spacecraft?

• The ISS has some magnetic protection; a Mars-bound craft leaves that region
• Earth's magnetic field removes every harmful particle near the ISS, so no shielding is needed there
• A Mars-bound craft stays inside Earth's magnetic field throughout its flight, just as the ISS does

Which observation is a possible technosignature for SETI researchers to investigate?

• An ordinary planet orbiting a star, with no evidence of technology in the observation
• An unusual radio signal or laser pulse that might come from technology
• A familiar natural star pattern whose only unusual feature is its name on an Earth map

A crew member feels homesick after a year with the same small crew, far from in-person contact with family. Which challenge does this illustrate most directly?

• Psychological isolation from separation and confined living
• Bone-density loss from reduced body loading during coasting flight
• Solar-radiation exposure beyond Earth's protective magnetic field

An astronaut exercises daily during a coasting Mars flight but still loses some bone density. Which explanation fits?

• Exercise in microgravity always stops bone loss, so the reported measurement must be impossible
• Gravity has vanished completely, so no force can act on the astronaut or the exercise equipment
• Microgravity reduces everyday loading; exercise may not fully offset bone loss

An astronaut sends a message from Mars. The signal takes 20 minutes each way, and Mission Control replies immediately. How many minutes after sending does the astronaut hear the reply?

According to the lesson, which pairing correctly describes both Rare Earth and the Great Filter as proposed explanations of the Fermi Paradox?

• Rare Earth: unlikely steps toward lasting spacefaring life; Great Filter: uncommon conditions for complex life
• Rare Earth: uncommon conditions for complex life; Great Filter: an unlikely step only in our future
• Rare Earth: uncommon conditions for complex life; Great Filter: an unlikely step in our past or future

A classmate says, 'SETI checked every possible signal from the whole galaxy, so no detection proves nobody else exists.' Which correction addresses the claim?

• All unusual radio signals are confirmed alien messages, even without checks for other sources
• Only some targets, signal types and times have been checked
• Radio waves cannot cross empty space, so telescope signals must come from Earth's atmosphere