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2021’s biggest space stories ranged from a rover landing on Mars to a new space telescope, a planetary-defense test, and the construction of China’s space station. “Biggest” is an editorial judgment, not an official ranking: the missions below were selected for scientific reach, technical firsts, human-spaceflight importance, and international significance. Some entries are launches; others are landings, ongoing operations, or preparation for a later flight.
Mars exploration
1. Perseverance landed in Jezero Crater
NASA’s Perseverance rover landed on Mars in 2021 and began investigating Jezero Crater. Among its early milestones was sealing its first rock core. The sample is intended for possible retrieval in a future NASA–European Space Agency (ESA) Mars Sample Return campaign; it was not returned to Earth in 2021.
2. Ingenuity made the first powered, controlled flight on another planet
Ingenuity, the small helicopter carried to Mars with Perseverance, demonstrated powered, controlled flight on another planet for the first time. Its technology demonstration was distinct from Perseverance’s rover science, though the two operated together on Mars.
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3. Tianwen-1 and the Zhurong rover marked China’s Mars arrival
China’s Tianwen-1 mission brought the Zhurong rover to Mars, a major national milestone described by the China National Space Administration (CNSA) as China’s first mark on the planet. The CNSA briefing supports the mission’s significance, but not a detailed chronology or operating-total account, so this entry focuses on its place in China’s Mars program rather than unverified dates or performance figures.
#1 Best Overall
Space telescopes and scientific missions
4. James Webb Space Telescope launched on Christmas Day
The James Webb Space Telescope (Webb) launched from Kourou, French Guiana, aboard an Ariane 5 rocket on 25 December 2021. It is a collaboration among NASA, ESA, and the Canadian Space Agency (CSA). Canada contributed the Fine Guidance Sensor (FGS), which helps the telescope point precisely, and the Near-Infrared Imager and Slitless Spectrograph (NIRISS). Webb’s launch was a genuine 2021 event; earlier projected dates were forecasts, not the final launch record.
5. Lucy began its asteroid mission
NASA’s Lucy spacecraft launched on 16 October 2021. It was one of the year’s scientific mission launches and is designed to study asteroids. NASA’s 2021 launch record and year-end review establish the launch and its scientific-mission status, but the sources cited here do not provide enough mission-specific detail to summarize its target sequence.
Rank #2
6. IXPE added X-ray astronomy to the year’s launches
NASA’s Imaging X-ray Polarimetry Explorer (IXPE) launched on 9 December 2021. The mission studies cosmic X-rays, extending the year’s headline science beyond planetary exploration.
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7. DART tested a planetary-defense technique
NASA’s Double Asteroid Redirection Test (DART) launched on 23 November 2021. NASA describes it as the world’s first planetary-defense test mission. That distinction matters: DART was a technology test, not an operational system protecting Earth from an imminent threat.
8. Landsat 9 continued the Earth-observation record
Landsat 9 launched on 27 September 2021, adding an Earth-observation mission to a year otherwise dominated in headlines by deep-space exploration. The launch record establishes when it flew; the sources cited here do not support a fuller account of its later data products.
Human spaceflight and station building
9. Crew-2 set a NASA-reported U.S. duration record
In NASA’s 2021 year-end account, the Crew-2 astronauts spent 199 days in orbit, which the agency described as a U.S. record at the time. NASA cited Crew-1’s 168-day stay as the previous mark. These are U.S. records as described by NASA, not claims about a global record.
10. China advanced construction of its space station
CNSA’s 2021 white-paper briefing identifies the Tianhe core module and sustained station construction as major achievements in China’s crewed space-station program. This makes China’s station-building effort an important part of the year’s human-spaceflight story. The briefing provides program context rather than a complete dated chronology, so it does not establish a specific 2021 mission date for this overview.
A major 2021 milestone that was not a 2021 launch
11. Artemis I preparation brought SLS and Orion together
NASA completed stacking the Space Launch System (SLS) rocket and Orion spacecraft on 21 October 2021. This was a significant preparation milestone for Artemis I, but the uncrewed lunar flight did not launch in 2021; NASA targeted it for 2022. Including Artemis here highlights how “space missions of 2021” can refer to preparation as well as missions that actually flew. If the list is restricted to missions launched during the year, this entry does not qualify.
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How to read a mixed list of 2021 missions
These entries do not share one measurable scale of importance. A useful comparison is what happened in 2021, what each effort set out to do, and whether its significance was scientific, technical, or human-spaceflight related.
| Mission or milestone | 2021 event | Primary significance |
|---|---|---|
| Perseverance | Mars landing and surface operations | Rover science and collection of a rock core for possible future sample return |
| Ingenuity | Flight demonstration on Mars | First powered, controlled flight on another planet |
| Tianwen-1 and Zhurong | Mars mission milestone | China’s Mars exploration and rover achievement |
| Webb | Launch | Internationally built space observatory |
| Lucy | Launch | Asteroid science mission |
| IXPE | Launch | Cosmic X-ray science |
| DART | Launch | Planetary-defense technology test |
| Landsat 9 | Launch | Earth observation |
| Crew-2 | Long-duration crewed flight | NASA-reported U.S. in-orbit duration record |
| Tianhe and China’s station program | Station construction program achievement | Human-spaceflight infrastructure |
| Artemis I | Launch-system preparation | Preparation for a later uncrewed lunar flight |
Together, the list shows why 2021 cannot be reduced to one kind of spaceflight. Mars operations, telescope and science launches, Earth observation, planetary defense, crewed missions, and station construction all mattered. The ordering is editorial, not a canonical ranking.
For context on China’s broader space program, CNSA’s 2021 briefing also reported 207 launch missions and a 96.7% Long March success rate across the preceding five years. Those figures cover that five-year period, not 2021 alone, and are not a ranking of the missions listed above.
Quick Recap
NASA Administrator Bill Nelson characterized NASA’s year this way: “From continuing to launch astronauts to the International Space Station from American soil to landing the Perseverance rover on Mars and logging the first flight on another planet, 2021 was a banner year for the world’s premier space agency and all of humanity,” The remark is NASA’s administrator’s assessment of the agency’s year, rather than an independent global ranking.
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