system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How were we able to get to the Moon within 9 years of going to space, but in the 42 years since we can't send someone to Mars?

Can you explain why it is so tough to get to Mars?  Why have we been able to send so many rovers but no people?  What is the biggest issues with sending someone there?  Is there a realistic time frame to getting there?
gpt
The quickest answer is that it's 250,000 miles to the moon; minimum distance to Mars is 50 million miles. 

Gravity on Mars is much greater, so the spacecraft has to be capable of generating a lot more lift to get off Mars.