Best in Space '24: A final flight, signs of Mars life and spaceflight milestones

In space, new boundaries were reached and amazing discoveries were made in 2024.

From Earth orbit to the fields of Mars to the moons of Jupiter, some incredible space exploration milestones were set during the past year. Here's a sampling of the best from 2024.

The little helicopter that could

When NASA's Perseverance rover touched down on the surface of Mars in early 2021, it wasn't alone. Tucked away in the rover's belly was a tiny twin-rotor helicopter nicknamed Ingenuity. Although Mars' atmosphere is composed of just a thin wisp of carbon dioxide, with only around 1 per cent of the density of Earth's atmosphere, scientists and engineers at NASA's Jet Propulsion Lab sent Ingenuity along on the mission as a test.

They'd gotten Ingenuity to fly in the lab's atmosphere simulator. However, could it actually fly in the Red Planet's thin atmosphere and across its challenging terrain? And if it did work, what would that mean for future Mars exploration?

Perseverance with Ingenuity Close Up April 2021 NASA JPL Caltech MSSS

The Perseverance rover captured this selfie of it and the Ingenuity helicopter in April of 2021, on "Wright Brothers Field" just before Ingenuity's first test flight. (NASA/JPL-Caltech/MSSS)

Not only did Ingenuity pass its tests, it aced the first five flights. In fact, it did so well that the JPL team gave it an official role in the Mars 2020 mission!

Acting as a aerial scout to locate science targets for Perseverance, Ingenuity completed a total of 72 flights over nearly three years. During that final, fateful flight, on January 18, 2024, both of its rotor blades were badly damaged during a hard landing, permanently grounding the little helicopter.

PIA26238 ingentuity ripples composite

This composite image shows the final position of Ingenuity, shot by Perseverance's SuperCam instrument. Bottom right, a zoomed view shows Ingenuity with its damaged rotor blades. Bottom left, a similar closeup reveals one of the rotor blade tips, located around 15 metres away from the helicopter. (NASA/JPL-Caltech/LANL/CNES/CNRS/Scott Sutherland)

According to the team at JPL, the reason Ingenuity had such a hard landing was because its on-board navigation computer couldn't properly idenfity the terrain it was flying over. It needed high-contrast terrain — rocks and pebbles, mainly — to help gauge its speed and height above the ground. However, the sand ripples it was flying over at the time were nearly featureless from its perspective.

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In essense, the sand created conditions where the helicopter was effectively flying blind. So, when it came down, it came down hard and at a bad angle. This resulted in the rotors clipping the nearest sand ripple, and at the high speed the rotors were spinning, all four rotor tips snapped off.

On January 25, NASA officially declared Ingenuity's scout mission to be over.

However, since the drone is otherwise functional and undamaged, NASA ordered it to continue taking pictures and collecting data, which it will continue to do for as long as its solar panels and batteries hold out.

One day, an astronaut from Earth may find Ingenuity and retrieve that data, adding to our knowledge about Martian weather and how dust and sand move across Jezero Crater. Furthermore, future Mars missions will likely include a similar helicopter, possibly outfitted with its own science instruments, to take our exploration of the Red Planet to new heights.

An unusual Martian rock spurs excitement

Has there ever been life on Mars? Well, in 2024, the Perseverance rover may have found an important clue to that mystery.

In July, while exploring an ancient dry river valley called Neretva Vallis, the rover happened upon 'Cheyava Falls', a rock that peaked the mission team's interest.

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Perseverance selfie at Cheyava - NASA JPL

A selfie shot by the Perseverance rover while at Cheyava Falls (the rock directly in front of the rover, with the bright clear patch and drill hole), in Neretva Vallis, on Mars. (NASA/JPL-Caltech/MSSS)

"Cheyava Falls is the most puzzling, complex, and potentially important rock yet investigated by Perseverance," Ken Farley, Perseverance project scientist of Caltech in Pasadena, said in a NASA press release at the time.

Three things made this particular rock such a compelling object of interest.

To sum up: The two long bands of light-coloured gypsum indicated that water once flowed through the rock. Organic compounds were detected in the darker reddish rock between the gypsum bands, something which can be left behind by living organisms. Additionally, the numerous 'leopard spots', which are light patches surrounded by deposits of iron and phosphate, are very similar to something found here on Earth, where living microbes use chemical reactions to produce energy, resulting in a patch of rock that changes colour from red to white, and becomes surrounded by a dark band of iron and phosphate released during those chemical processes.

Perseverance Finds Cheyava a Rock with Leopard Spots - annotated

This closeup and enhanced view of Cheyava Falls reveals the gypsum and olivine bands, along with the 'leopard spots' that make this discovery so important. (NASA/JPL-Caltech/MSSS)

If each of these three things were found separately, they wouldn't have caused much of a stir. However, found together like this, they add up to something much more significant. This isn't definitive proof that there was once life on Mars, but it might be the closest we've come, yet.

Pushing the boundaries of human space exploration

From stranded astronauts to leakes on the space station, so much has been going on with humans in space this year. Perhaps the most important story in human space exploration for 2024, though, was the Polaris Dawn mission.

Lead by billionaire philanthropist Jared Isaacman, Mission Pilot Scott "Kidd" Poteet, Mission Specialist Sarah Gillis, and Mission Specialist/Medical Officer Anna Menon spent nearly five days in space. During that time, amid normal daily activities and enjoying the view out of the windows, they conducting a total of 36 different scientific experiments.

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More importantly, though, they also set two new milestones in human spaceflight.

First, their initial orbit took them to a distance of 1,400 kilometres away from Earth. Apollo astronauts travelled farther away to reach the Moon. However, specifically for missions orbiting Earth, this is the farthest ever achieved by a human crew. Prior to this, the record was 1,374 km, set by the Gemini 11 crew back in 1966.

Polaris Dawn Orbit - SpaceX

This graphic shows the distances the Polaris Dawn mission will be from Earth during two mission objectives, compared with the altitude of the International Space Station and SpaceX's first private mission, in 2021, Inspiration4. (SpaceX)

Second, once Resilience had settled into a closer orbit, at an altitude of around 700 km, Isaacman and Gillis became the first civilians to ever leave their spacecraft and perform a spacewalk. Up until this point, every astronaut to perform a spacewalk was employed by one of the world's government space agencies. While the two were, technically, only in space from their waist up, Isaacman spent just shy of 8 minutes performing mobility tests on his spacesuit. Gillis following that up with a little over 7 minutes of similar tests, and in the process become the youngest person ever to perform a spacewalk (at age 30).

During the spacewalk, which took over 26 minutes from hatch opening to hatch closing, the entire capsule and crew were exposed to the vacuum of space.

This was a small step, of course. However, it could mark the start of a new era in human spaceflight — one where we see more civilians living and working in space, followed by the Moon, and then beyond.

BONUS: Io's 'smooth as glass' lava lake

For the past eight years, NASA's Juno spacecraft has been zooming around giant Jupiter. By the end of 2024, it will have made a total of 68 close passes around the planet, snapping pictures of its cloud tops and using gravity to map its interior structure.

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Juno at Ganymede illustration teaser NASA JPL-Caltech SwRI MSSS Kalleheikki Kannisto

This artist's conception drawing shows the Juno spacecraft passing Jupiter's giant moon, Ganymede. (NASA/JPL-Caltech/SwRI/MSSS/Kalleheikki Kannisto)

Since mid-2021, the mission team has been altering Juno's path around the planet to have the spacecraft rendezvous with three of Jupiter's largest moons. It began with Ganymede, followed by Europa in late 2022, and then four passes by Io, the innermost of the four moons.

During Juno's latest pass by Io, in February 2024, its camera captured unprecedented details of the moon's terrain features from just 1,500 kilometres above its surface. One of the features that stood out, in particular, was a "smooth as glass" lava lake.

Loki Patera Lava Lake Glassy Surface Io Juno Zoom NASA JPL SwRI MSSS GeraldEichstädt ThomasThomopoulos

This JunoCam image of Loki Patera was captured in February 2024 during Juno's 58th flyby of Jupiter. The brightness of the feature is caused by sunlight reflecting off the frozen lava surface, in the same way that light is reflected by a mirror (specular reflection). (NASA/JPL-Caltech/SwRI/MSSS/Gerald Eichstädt/Thomas Thomopoulos)

"We got some great close-ups and other data on a 200-kilometre-long lava lake called Loki Patera. There is amazing detail showing these crazy islands embedded in the middle of a potentially magma lake rimmed with hot lava," Scott Bolton, the principle investigator for the Juno mission, explained. "The specular reflection our instruments recorded of the lake suggests parts of Io's surface are as smooth as glass, reminiscent of volcanically created obsidian glass on Earth."

Io is the most volcanically active object in the solar system. Squeezed and stretched by the competing gravity of Jupiter and the other three Galilean moons, the inside of Io is heated up by the resulting friction. This has caused volcanic eruptions and lava flows, which rework and change Io's surface over time.

While these have been captured by various spacecraft and telescopes in the past, never before have we seen such a close-up look at the results.

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