The Rosetta mission, launched by the European Space Agency (ESA), was a groundbreaking space mission that captured the world’s attention for its bold ambition: to chase down a comet, land on it, and study it in unprecedented detail. This mission, which launched in March 2004, marked the first time a spacecraft had successfully orbited and landed on a comet, providing crucial insights into the early solar system.

This is the remarkable story of the launch and journey of the Rosetta mission and its impact on our understanding of comets and the formation of our solar system.

Mission goals and objectives

Named after the Rosetta Stone, which helped decipher ancient Egyptian hieroglyphs, the mission was designed to help scientists unlock the secrets of comets, which are often described as «cosmic time capsules». These icy, rocky bodies are remnants from the early solar system and could hold clues to the origin of water and organic compounds on Earth.

Rosetta’s primary goals included:

• Orbiting Comet 67P/Churyumov–Gerasimenko to study its surface and behavior as it approached the Sun.
• Deploying a lander, named Philae, to the surface of the comet for close-up analysis.
• Gathering data on the comet’s composition, structure, and activity to better understand how comets evolve and what role they might have played in bringing water and life-building molecules to Earth.

The launch of Rosetta

Rosetta’s journey began on March 2, 2004, when it launched aboard an Ariane 5 rocket from Kourou, French Guiana. The launch itself was a massive engineering feat. Rosetta’s journey to Comet 67P was no simple path; it required multiple gravity-assist maneuvers to gain enough speed to reach its target.

These maneuvers involved flybys of Earth and Mars over a period of several years, using the gravitational pull of these planets to slingshot the spacecraft deeper into space. This complex trajectory allowed Rosetta to conserve fuel while picking up the necessary speed to intercept Comet 67P.

A 10-year journey through space

After its launch, Rosetta embarked on a 10-year journey through space. During this time, it completed three flybys of Earth and one of Mars, as well as two asteroid flybys—2867 Šteins in 2008 and 21 Lutetia in 2010—allowing it to study these objects and test its instruments.

In 2011, as it continued its trek toward Comet 67P, Rosetta entered a 31-month hibernation phase to conserve energy. During this period, most of the spacecraft’s systems were shut down, except for its computer, which kept track of time and ensured that Rosetta would awaken at the right moment.

On January 20, 2014, Rosetta successfully «woke up» from its long hibernation, much to the relief of the ESA team and space enthusiasts around the world. This marked the beginning of the final phase of its journey toward the comet.

Rendezvous with comet 67P/Churyumov–Gerasimenko

After a decade in space, Rosetta finally reached its destination. In August 2014, the spacecraft entered orbit around Comet 67P/Churyumov–Gerasimenko, becoming the first spacecraft to do so. The images sent back to Earth revealed the comet’s bizarre, rubber-duck-shaped structure, which surprised scientists and added a new level of complexity to the mission.

Rosetta began mapping the surface of the comet, analyzing its composition, and monitoring its activity as it approached the Sun. The data gathered during this phase helped scientists understand how the comet’s surface changed as the solar radiation caused its ice to sublimate, forming the characteristic coma and tail.

The historic philae landing

Perhaps the most ambitious part of the Rosetta mission was the deployment of its Philae lander. On November 12, 2014, Philae made history as the first human-made object to land on a comet. However, the landing didn’t go exactly as planned.

Upon contact with the comet’s surface, Philae’s harpoons, designed to anchor it to the surface, failed to fire, causing the lander to bounce twice before settling in a shaded area. This prevented Philae from receiving enough sunlight to recharge its batteries, limiting its operational time to about 60 hours.

Despite the challenges, Philae was able to send back a wealth of data during its short active period, including the first-ever in situ measurements of a comet’s surface. Philae’s instruments analyzed the composition of the comet’s dust and ice, confirming the presence of organic molecules that could be the building blocks of life.

Scientific discoveries and impact

The Rosetta mission yielded an enormous amount of data, transforming our understanding of comets. Some of the most significant discoveries include:

1. Organic molecules: Rosetta detected complex organic molecules on Comet 67P, including amino acids and sugars, suggesting that comets may have played a role in delivering life-building compounds to Earth.
2. Water on comets: One of the mission’s key goals was to determine whether the water on comets was similar to that on Earth. Surprisingly, Rosetta found that the deuterium-to-hydrogen ratio in Comet 67P’s water was different from that of Earth’s oceans, suggesting that comets like 67P may not have been the primary source of Earth’s water.
3. Comet activity: Rosetta closely monitored the changes in Comet 67P as it approached the Sun. The mission provided valuable insights into how comets become more active, shedding gas and dust to form their glowing comas and tails.
4. The structure of comet nuclei: Data from the mission showed that Comet 67P had a porous structure, composed of loosely packed dust and ice. This finding helped scientists understand how comets formed in the early solar system.

The end of the Rosetta mission

After two years of orbiting Comet 67P and gathering vast amounts of data, Rosetta’s mission came to an end on September 30, 2016. In a carefully planned descent, the spacecraft was intentionally crash-landed on the comet’s surface, bringing the mission to a close. Even in its final moments, Rosetta continued to send back valuable data as it approached the comet.

Legacy of the Rosetta mission

The Rosetta mission was a monumental achievement in space exploration, showcasing the incredible potential of international collaboration, cutting-edge technology, and human curiosity. The data collected has not only expanded our understanding of comets but also offered crucial insights into the early solar system and the origins of life on Earth.

Rosetta’s success has inspired a new generation of missions focused on small bodies in the solar system, including NASA’s OSIRIS-REx mission to the asteroid Bennu and Japan’s Hayabusa2 mission to the asteroid Ryugu. These missions, building on Rosetta’s legacy, continue the quest to unlock the secrets of the solar system’s formation and evolution.

The Rosetta mission will forever be remembered as one of the most ambitious and successful space exploration endeavors, proving that with ingenuity and determination, humanity can reach even the most distant corners of our cosmic neighborhood.