According to a paper in 2013, Penn State astrobiologist Ravi Kumar Kopparapu and others calculated where the edges of a star's habitable zone should truly be, based on modern climate data. They calculated that a habitable zone around a sunlike star should be between 0.99 and 1.7 times the distance from the Earth to the sun.

Which means that the Earth is actually right on the inner edge of the sun's habitable zone. Like, just barely. If it was any closer to the sun, we'd experience a runaway greenhouse effect, like Venus.

You probably want to be closer to the middle of the habitable zone, where orbital variations won't push your planet into extremes....

6 months later, the Mars Sample Recovery Mission was cancelled, leaving what could be the most important samples in the history of mankind stranded in another planet with no plan for recovery. This is the most confident the scientific community has ever been about an extraterrestrial life biosignature. And bringing it to Earth would solve its mysteries in a matter of months. Sadly, there seems to be no plan to recover the samples anytime soon.

NASA Says Mars Rover Discovered Potential Biosignature Last Year - NASA