https://mars.nasa.gov/technology/helicopter/
(Plain Text Version)
New Ways to Explore the Red Planet
Today, the standard method of exploring the surface of the Moon or a planet is to land a robotic crawler loaded with cameras and scientific instruments. In my review of space missions, I was surprised to learn that these vehicles were very rare before the 21st century.
A Bit of History
In the beginning of the Space Age, missions were quite simple by today’s standards. The first lunar missions used a rather obvious procedure: transmission of data before collision with the Moon.
The first few years of space exploration were plagued by all sorts of problems. For every success, there were several failures.
Here is a timeline of the milestones:
1957: Sputnik 1, the first artificial satellite was launched.
1959: Luna 2 returned data before lunar impact.
1966: Luna 9 made first soft landing on the Moon, and returned photos and radiation data.
1969: Astronauts aboard Apollo 11 landed on the Moon.
1970: First of two Lunokhod missions landed on the Moon, and deployed the first robotic crawler to operate away from Earth.
1997: The Mars Pathfinder crawler was deployed on Mars and functioned for more than two months.
2004: Two vehicles were deployed on Mars, and functioned for a long time: Spirit (6 years) and Opportunity (15 years).
In summary, 4 decades elapsed from Sputnik 1 before remote crawlers became commonplace.
2021: Will It Fly?
We are on the verge of another major step in exploring our neighboring bodies: within a few days, Ingenuity, the first Martian helicopter will be flight-tested.
For a successful flight, many challenges need to be overcome, such as generating enough lift in the ultra-thin Martian atmosphere, and controlling the craft with limited human interaction.
Ingenuity has tested its rotating blades at low speed, and is scheduled to fly on Sunday, April 11. For details, see:
Real Simple Astronomy 
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