Mars is welcoming three ambitious missions from the UAE, China, and the US in February 2021—the busiest period in decades. Here's why they're converging now.
The Red Planet is experiencing its most intense influx of visitors in 47 years. The UAE's Hope orbiter successfully entered Mars orbit on February 9, aiming to study the planet's dynamic atmosphere and weather patterns.
On February 10, China's Tianwen-1 mission followed suit, achieving orbit and preparing its rover for a landing in May. Key goals include mapping water ice distribution in the subsurface and detailing Mars' geological structure.
Finally, NASA's Mars 2020 mission will land the Perseverance rover in Jezero Crater on February 18. Over at least two years, it will hunt for signs of ancient microbial life in a former river delta.
Three missions, three nations—but no coincidence. This "Mars rendezvous" stems from precise orbital timing.
Imagine Earth and Mars as runners on concentric tracks around the Sun: Earth on the inner lane (365-day orbit), Mars on the outer (687 days). Earth periodically laps Mars, aligning every two years at about 62.1 million kilometers apart.
Missions don't launch at opposition; instead, they depart months earlier when Earth trails Mars, enabling an efficient Hohmann Transfer Orbit. Pioneered by engineer Walter Hohmann in 1925, this fuel-saving path minimizes energy needs.
The animation below illustrates the Hohmann transfer used by NASA's InSight lander, which arrived in 2018.
This optimal launch window—cutting travel time and fuel—opens roughly every 26 months for a few weeks. The latest, last summer, saw Hope launch July 19, 2020; Tianwen-1 on July 23; and Perseverance on July 30.
That's why these missions arrive nearly simultaneously.
The European Space Agency (ESA) and Roscosmos planned ExoMars for the same window but delayed to 2022 due to parachute issues.
Orbital traffic isn't new—1973 saw four Soviet probes (mostly unsuccessful), following partial successes in 1971. But 2021 stands out for diversity and active hardware.
NASA operates three orbiters; ESA has two (one joint with Roscosmos); India has one. On the surface, Curiosity rover and InSight lander remain operational.
