Mars exploration took some big steps forward in 2021.
During this very eventful year, two nations joined the Mars club, a helicopter plied Red Planet skies for the first time ever and humanity kicked off an ambitious interplanetary sample-return campaign.
A lot of the action took place in February, which saw the arrival of three high-profile missions at the Red Planet. The United Arab Emirates' Hope mission, the Arab world's first interplanetary effort, slipped into orbit around Mars on Feb. 9.
A day later, Tianwen 1, China's first fully homegrown Mars mission, followed suit. And on Feb. 18, NASA's car-sized Perseverance rover touched down inside the Red Planet's Jezero Crater. (Earth and Mars align properly for interplanetary launches just once every 26 months. The last such window opened in summer 2020, which explains why these three missions all reached Mars around the same time.)
Related: A brief history of Mars missions
All three missions are still going strong. Hope continues to scrutinize Mars' atmosphere, gathering data that will help scientists better understand the planet's weather and climate.
Tianwen 1 is hunting for buried water ice, mapping out Mars' magnetic field and analyzing the composition of surface rocks, among other tasks. And in May, a rover named Zhurong separated from the orbiter and touched down successfully on the huge Martian plain Utopia Planitia.
The landing was a huge milestone for China, which had put two rovers down on the moon but had never before pulled off an interplanetary touchdown. Zhurong is looking for water ice and gathering geological and climate data, among other tasks. The rover has also snapped a few striking selfies as it has rolled across Utopia Planitia's vast expanse.
Perseverance is hunting for signs of ancient Mars life in the 28-mile-wide (45 kilometers) Jezero Crater, which harbored a big lake and a river delta billions of years ago. The six-wheeled robot is also collecting and caching samples that will be returned to Earth, perhaps as early as 2031, by a joint NASA-European Space Agency (ESA) campaign.
Perseverance carries 43 sample tubes and has sealed up six of them to date, mission team members have said.
The big rover didn't travel to Mars alone; it flew with a 4-pound (1.8 kilograms) helicopter named Ingenuity attached to its belly. Shortly after the duo landed, Ingenuity embarked on five pioneering flights above Jezero's floor, showing that aerial exploration is possible on Mars despite the relative wispiness of the planet's atmosphere. (Mars' air is just 1% as dense as that of Earth at sea level.)
That was supposed to be it for the technology-demonstrating Ingenuity. But NASA granted the little chopper an extended mission, and it's now flying scouting sorties for Perseverance. To date, Ingenuity has performed 18 flights on Mars, racking up more than 30 minutes of air time and covering 2.37 miles (3.81 km) of ground.
"The helicopter has become a real asset and partner to our science team," Perseverance surface operations mission manager Jessica Samuels, of NASA's Jet Propulsion Laboratory (JPL) in Southern California, said in a video about the rover and helicopter that JPL posted on YouTube on Dec. 28.
The new arrivals aren't the only robots studying Mars up close, of course. NASA's Curiosity rover has been exploring the 96-mile-wide (154 km) Gale Crater since August 2012, for example, and the agency's marsquake-detecting InSight lander recently marked three years on the Red Planet.
Then there are the orbiters. NASA's Mars Odyssey, Mars Reconnaissance Orbiter and MAVEN (Mars Atmosphere and Volatile Evolution) probe have been circling the planet since 2001, 2006 and 2014, respectively. India's Mars Orbiter Mission arrived about the same time as MAVEN.
ESA's Mars Express has been circling Mars since late 2003. And the Trace Gas Orbiter — part of the ExoMars program, a joint effort of ESA and Russia's federal space agency Roscosmos — arrived at the Red Planet in October 2016 to sniff for methane and other low-abundance gases in the planet's air.
Mike Wall is the author of "Out There" (Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or on Facebook.