It may seem like a lie, but when the Earth was formed, 4.5 billion years ago, temperatures here were much higher than in Piauí. So high that all the water would have evaporated and been lost into space. So, if the Earth couldn’t retain it, where did all this water that now covers two-thirds of our planet come from? This is just one of the intriguing questions the Rosetta Mission sought to answer when it was sent to study a comet up close. But this mission ended up becoming a true space odyssey that presented us with spectacular images, in addition to revealing surprising secrets about these cosmic travelers and the origins of the Solar System.
(Comet 1P/Halley recorded by Giotto in 1986 – Credits: ESA/MPS (HU Keller)/Daniel Macháček)
The idea of studying a comet up close began to take shape in the 1980s with the Giotto Mission. This pioneering ESA mission flew past Halley’s Comet in 1986, passing through the comet’s tail and returning the first close-up images of a comet nucleus. The success of Giotto paved the way for even more ambitious missions, and in 1993, ESA assembled a team of scientists and engineers from around the world to develop the Rosetta Mission. Named after the Rosetta Stone, which made it possible to interpret Egyptian hieroglyphics, the Rosetta probe would be tasked with deciphering what comets have to tell us about the formation of the Solar System and the origins of water here on Earth.
Rosetta was launched in March 2004, aboard an Ariane 5 rocket, departing from the Kourou Space Center, in French Guiana. Its destination: Comet 67P/Churyumov-Gerasimenko, an icy traveler that orbits the Sun every six and a half years between the orbits of Jupiter and Earth.
(Comet 67P/Churyumov-Gerasimenko and its peculiar rubber ducky shape – Image: ESA/Rosetta/Reproduction Twitter)
67P/Churyumov-Gerasimenko, or “Rubber Duck Comet” to those close to you, is not just any comet. With a peculiar shape that earned it its nickname, 67P is a relatively small celestial object, just over 4 km in diameter, but which holds valuable secrets about the composition and conditions of the early Solar System.
Comets are believed to be “leftovers” from the formation of the Solar System, frozen pieces of dust and ice that have been preserved practically intact since the time the Sun and planets formed. By studying the chemical composition and internal structure of 67P, the Rosetta mission could provide important clues about the formation of planets and the origins of water on Earth.
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But Rosetta’s journey to comet 67P wasn’t exactly a walk in the park. It was a true space odyssey, a ten-year journey that took her billions of kilometers, crossing the asteroid belt and performing complex gravitational assistance maneuvers with Earth and Mars to propel the probe towards its destination.
During its visit to the Red Planet in 2005, Rosetta made its riskiest maneuver: a flyby just 250 km from the Martian surface, passing through the night side of the planet. During this maneuver, the probe needed to be placed in hibernation mode, as its solar panels would not receive energy and as a result, Rosetta was without communication with Earth for 15 minutes. A maneuver so risky that it became known as “The One Billion Euro Bet”.
(Rosetta’s “Selfie” on its passage through Mars in 2007 – Credits: ESA/Rosetta/Philae/CIVA)
Later in 2007, during its penultimate gravitational assist with Earth, the probe once again raised concerns among astronomers. This time, not because of a dangerous maneuver, but because Rosetta was mistakenly identified as an asteroid measuring around 20 meters that could hit our planet on November 13 of that year (“asteroid” 2007 VN84). Fortunately, the confusion was resolved before the “apocalypse gang” could record a video announcing yet another end of the world. And so Rosetta passed by Earth, receiving a valuable gravitational boost that would take it to Comet 67P.
But not before crossing the Main Asteroid Belt, where he visited two inhabitants of those bands, the asteroid Steins, in 2008, and Lutetia, in 2010, sending spectacular images and valuable data about these primitive celestial bodies. But the big challenge was yet to come.
In August 2014, after a long journey, Rosetta finally reached its destination: comet 67P. Since the approach, the images sent by the probe have surprised and excited scientists. Comet 67P seemed like a much more complex world than its discoverers (Klim Ivanovych Churyumov and Svetlana Ivanovna Gerasimenko) named. In addition to its aforementioned rubber ducky shape, scientists discovered the comet’s steep cliffs, deep craters, dusty plains and jets of gas and dust that were expelled from its surface as the comet approached the Sun. This terrain surprisingly accident would make the next phase of the mission even more challenging.
The Rosetta Mission had an ace up its sleeve: the Philae probe, a landing module that would be ejected from Rosetta and attempt to land on the surface of comet 67P, an unprecedented feat in the history of space exploration.
On 12 November 2014, the world held its breath as Philae separated from Rosetta and began its slow descent towards the comet’s surface. The landing, broadcast live by ESA, was a moment of great excitement and apprehension.
Due to the low gravity and the slightly harder and more uneven surface than expected, Philae ended up bouncing around the comet a few times before settling in an area with little sunlight. Despite the setbacks, Philae managed to carry out most of its scientific experiments, sending back valuable data on the composition of 67P’s soil before going into hibernation due to lack of power.
(Philae, in the right corner of the image, after bouncing off the comet and stopping, tipped over, in a region with low sunlight – Credits: ESA/Rosetta/MPS)
Over the course of two years, Rosetta orbited comet 67P, tracking its activity as it approached the Sun and then moved away again. The probe collected unprecedented data on the comet’s chemical composition, revealing the presence of water, carbon dioxide, carbon monoxide, methane, ammonia and other complex organic molecules. This reinforced the idea that comets are like space freezers, which preserve the ingredients left over from preparing the Solar System.
Analyzes of the water present in comet Churyumov-Gerasimenko showed that its isotopic composition is different from the water found in Earth’s oceans, contradicting the theory that our planet’s water originated in comets.
(Comet 67P Churyumov-Gerasimenko recorded by Rosetta in 2015 – Credits: ESA/Rosetta/MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA/D. Machacek)
With 67P moving away from the Sun and solar power dwindling, ESA decided to end the mission in spectacular fashion. On September 30, 2016, the Rosetta probe performed a controlled landing on the surface of comet 67P, sending high-resolution images and scientific data until the last moment.
The Rosetta mission marked a new era in space exploration, demonstrating humanity’s ability to reach and study complex and challenging celestial objects such as comets. The data collected by Rosetta and Philae continue to be analyzed by scientists around the world, helping us better understand the origins of the Solar System, water and even life on Earth.
Rosetta’s odyssey, just like the Rosetta Stone. which inspired its name, helped us to decipher part of the history of our past and to better understand the place we occupy in this vast cosmic ocean. The mission, which brought together scientists and engineers from around the world, proved that international cooperation and the search for knowledge are essential for the advancement of humanity. May the Rosetta saga continue to inspire future generations to explore the cosmos and unlock the secrets of the universe!
