If all goes well, we're about to see the first-ever helicopter on another planet. At least, any built by humans.
NASA's Mars 2020 mission enters its most crucial phase on Friday morning (NZ time) - landing on the red planet. Just before 10am the spacecraft carrying the Perseverance rover and Ingenuity helicopter drone will enter the Martian atmosphere and attempt to drop off its US$2.7 billion cargo.
Rather than descend from the relative safety of orbit, Perseverance - which weighs a tonne - will attempt to enter Martian space and land in one go.
"Hopefully it will not be a crash-landing," Kiwi space expert Matthew Pavletich told The AM Show on Friday.
"A lot of designs of spacecraft, depending on how big they are, would enter Martian orbit first, then land later on - but that requires a lot of fuel. So they're maximising the downmass (payload) to the surface by encasing it all in a big heat shield."
The ship will use rocket thrusters and a parachute to slow down from 20,000km/h to walking pace.
"The biggest risk is probably at the 99.9 completed descent part - it has to break out of the heat shield, hovers about 20m above the ground to make sure the terrain is friendly, then it lowers the rover on a set of cables," said Pavletich.
"The moment the wheels touch the ground, the cables are severed and the rocket... flies over the hill and crashes somewhere. That's the most dangerous part - will the cables separate? Because if they don't, it'll pull the thing with it and tip it over, which would be a very bad day at the office."
Fewer than half of all attempts to land on Mars to date have been successful. NASA has a good track record though - its only failure, in 1999, happened because of confusion between NASA's metric units and manufacturer Lockheed Martin's imperial.
Perseverance is an upgraded version of NASA's 2012 rover Curiosity, which has long outlived its planned two-year mission.
Curiosity looked at whether its location - the Gale crater - could ever have once supported life. Perseverance will look for signs of life itself in the Jezero Crater, which is believed to once have held a giant lake.
"This is the first dedicated mission since 1976, when NASA's Viking landers landed to look for life," said Pavletich. "It's unlikely you'll find life near the surface dirt - the atmospheric pressure on mars is very low, the water is only there a metre, two metres, three metres below the ground. If there is any life on Mars it'll probably be anaerobic bacteria they found some day."
Perseverance will collect samples and store them in sealed containers, to be collected by a follow-up mission.
In addition to digging in the Martian dirt, the Mars 2020 mission includes a helicopter drone called Ingenuity. It's first launch is in about a month, and is expected to fly about three to five metres above the ground up to 50m away from Perseverance.
While largely just a test and demonstration of the technology, it's hoped Ingenuity will be able to snap images of places Perseverance can't reach and scout out potential new places to explore.
Live coverage of the landing attempt begins at 8am. The landing is scheduled for around 9:55am - at least that's when signals from Mars will arrive on Earth, about 11 minutes after they actually happen.