A mission poster for Rosetta.

Image Credit: ESA/ATG medialab; Comet image: ESA/Rosetta/NavCam

An image from the "Once Upon a Time" cartoon series

Image Credit: ESA

Rosetta's last image of Comet 67P/Churyumov-Gerasimenko, taken shortly

before impact, at an estimated altitude of about 20 m above the surface.

Image Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA.

It’s the beginning of a story that draws you in, but it’s the ending that leaves you lingering, forever connected to the characters. At least if it’s a good story. The fairy tale of Rosetta and Philae , the first spacecraft and lander to rendezvous with a comet and travel with it in orbit around the sun, came to a close early Saturday morning (EDT) in a well-crafted ending.The story of their long journey to comet 67P/Churyumov-Gerasimenko and two years of exploration is captured brilliantly in a series of cartoon videos made by the European Space Agency. The plot features a perilous journey into the unknown, a long and deep sleep, a tricky landing, a period of disorientation, the ultimate sacrifice, and the endearing connection between a spacecraft, lander, and mission control. If you’re not familiar with the mission: Go, watch fans may prefer the commissioned short film Ambition that takes a sci-fi approach, along with the recently released Ambition-Epilogue The characters enthralled the public, with the video series earning Rosetta and Philae hundreds of thousands of Twitter followers. It’s not just a story of effective public engagement though, it’s a story of more than 20 years of amazing science, engineering, and discovery. Approved in 1993, Rosetta was a European Space Agency mission that included contributions from its member states and NASA. It launched in 2004 on a 10-year trip that included flybys of the Sun and Mars and a two-year hibernation, before finally arriving at 67P/Churyumov-Gerasimenko in the middle of 2014.Like all good stories, it is a tale of self-discovery. Maybe not so much for Rosetta, but for the scientists, engineers, and visionaries that turned her into a reality and for the public that supported the ride. The goal of the mission was to find out more about the early solar system and the impact of comets on our existence. For example, might comets be responsible for depositing water or other elements essential for life on the Earth? After all, they are made of ice, dust, rocks, and organic compounds.After a few months of data gathering, Philae separated from Rosetta and landed on the comet’s surface in November of 2014. Philae’s rough landing took a toll, but he still sent back the first set of data from a comet’s surface. Rosetta explored the comet from a distance until September 30, 2016, recording its activity and response to the rise in temperature as it approached the sun. She flew through its clouds of dust and took data on its water vapor, chemical composition, gravity field, surface features, and environment. Ever the photographer, she documented the comet from all angles and revealed a surprising shape that is likely the result of a collision of two different comets.Analyzing the wealth of data will take time—lots of time—but there have already been some important results. One of Rosetta’s primary aims was to study water, given the theory that water on Earth came at least partially by way of a comet. However, an analysis of water on 67P/Churyumov-Gerasimenko shows a very different molecular makeup than water on Earth. This is evidence that asteroids, not comets, may be primarily responsible for our oceans. An analysis of samples collected by Philae during its touchdown show sixteen organic compounds, including four that haven’t been found on a comet before. They don’t indicate the presence of life, but some of them are ingredients for life.The mission came to a close on Saturday when Rosetta met the comet in a controlled impact. She sent up-close-and-personal images of its surface until the very end. Her final resting place is not far from Philae, the two companions reunited in the end. The information they collected will be studied for years, providing important insights into our history. As the Ambition-Epilogue says, “In September 2016, Rosetta’s journey ends. We continue ours.”