“Spot the differences” to assist in revealing Rosetta image secrets

This series of images of Comet 67P/Churyumov–Gerasimenko was captured by Rosetta’s OSIRIS narrow-angle camera on 12 August 2015, just a few hours before the comet reached the closest point to the Sun along its 6.5-year orbit, or perihelion. The image at left was taken at 14:07 GMT, the middle image at 17:35 GMT, and the final image at 23:31 GMT.  The images were taken from a distance of about 330 km from the comet. The comet’s activity, at its peak intensity around perihelion and in the weeks that follow, is clearly visible in these spectacular images. In particular, a significant outburst can be seen in the image captured at 17:35 GMT. Credit: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Today, ESA and Zooniverse unveil Rosetta Zoo, a citizen science project inviting volunteers to participate in a cosmic “spot the difference” game. By perusing images acquired by the ESA’s Rosetta project, you can help scientists determine how the surface of a comet changes as it orbits the Sun.

Between 2014 and 2016, Rosetta spent over two years orbiting Comet 67P/Churyumov–Gerasimenko. The spacecraft conducted an in-depth investigation of the comet, gathering unparalleled data to solve some of the most perplexing riddles surrounding the genesis and evolution of our solar system. During a portion of Rosetta’s research, the comet approached the Sun, a phenomenon known as perihelion. Following its closest approach of approximately 186 million kilometers to our star, the comet retreated. Consequently, its surface was lit in various ways throughout Rosetta’s voyage.

Rosetta saw a variety of landscape changes on Comet 67P, including the dramatic collapse of cliffs, the development of pits, and the evolution of dust patterns and rolling boulders. As sunlight warms the ice and dust surrounding the nucleus of a comet, scientists are interested in using these changes to investigate the mechanism by which the comet sheds its outer layers.

However, the sheer quantity of surface changes makes documenting them a difficult process. So scientists need your assistance.

The movement of a 30-meter-wide boulder over approximately 140 meters. From El-Maarry and others (2017)

Massive volumes of data require a massive number of eyes.

“The Rosetta archive, which is widely accessible to scientists and the general public, comprises a large amount of data acquired by this incredible mission that has only been partially studied,” explains Bruno Mern, director of the ESAC Science Data Centre near Madrid, Spain.

“In the past few years, astrophotographers and space enthusiasts have discovered changes and indications of activity in the photographs of Rosetta. Due to the absence of human eyes filtering through the entire information, it has not been able to link any of these events to surface changes, with the exception of a few isolated instances. We certainly require extra eyeballs!”

This is why ESA teamed with Zooniverse, the largest and most popular crowdsourced research platform in the world. The new Rosetta Zoo project presents a specific set of data: pairs of images captured by Rosetta’s OSIRIS camera before and after perihelion of Comet 67P’s surface.

Volunteers are asked to compare photographs of roughly the same region and notice a number of changes, including large-scale dust transport and the movement or disappearance of comet fragments. At times, this may necessitate zooming in or out multiple times or rotating the photos to detect changes at various scales, bringing the iconic comet up close and personal.

Sandor Kruk, a postdoctoral researcher at the Max Planck Institute for Extraterrestrial Physics near Munich, Germany, who conceived and initiated the project during his ESA research fellowship a couple of years ago, explains: “Given the complexity of the imagery, the human eye is much better at detecting small differences between images than automated algorithms are.”

“The OSIRIS archived photographs have been accessible to the public for some time, but many images have not yet been evaluated for changes in the comet’s surface. This is why we decided to establish this citizen science project and encourage volunteers to examine photos of 67P captured by Rosetta. Given the excitement that Rosetta’s mission aroused, we hope that many members of the public would join this project to assist scientists in analyzing its data.”

Poster for the Rosetta mission depicting the landing of the Philae lander on comet 67P/Churyumov–Gerasimenko. The image of the comet was captured by Rosetta’s navigation camera (ESA/Rosetta/NavCam). Image courtesy of ESA/ATG medialab; comet image courtesy of ESA/Rosetta/Navcam

Your input will enhance our comprehension of the solar system.

The initiative will provide maps of changes and active areas on the comet’s surface, with labels for each sort of change, thanks to the visual observation of numerous volunteers. Then, scientists will be able to correlate the comet’s activity with changes on its surface, establishing new models to link the physics of comet activity to observed changes such as the lifting of boulders or the fall of cliffs.

By sifting through Rosetta’s images and participating in a cosmic game of “spot the difference,” you will assist us in gaining a deeper understanding of comets and the solar system as a whole. But the benefits are reciprocal: by releasing these data to the public, we seek to increase the transparency of our work, increase citizen participation in scientific research, and forge deeper ties between science and society.

Anyone can use Rosetta Zoo online without registering, installing an app or application, or having any prior scientific knowledge. Identify the differences between as many or as few image pairs as you have time for, be it five minutes while waiting for the bus or recurring evenings of cometary research.

“How does a primitive comet appear? No one knows, but with the help of volunteers we can characterize how comets evolve now and understand the physics driving those changes: then we can rewind the film of cometary evolution all the way back to the beginning of the solar system “Jean-Baptiste Vincent, a planetary scientist at the DLR Institute of Planetary Research in Berlin, Germany, explains.

Source: European Space Agency