A recent study published in Science Today summarizes the changes observed during two years of Rosetta at Comet 67P/Churyumov-Gerasimenko. A notable difference can be seen in captured images of before and after the comet's most active period - perihelion - as it reaches its closest point to Sun along its orbit.
According to ESA, Ramy El-Maarry, study leader says that monitoring the comet continuously helped them look at the changes a comet goes through as it traversed the inner solar system. It also helped the researchers give an insight of how comets change when they travel closer to the sun and how fast these changes take place. Images received from Rosetta's OSIRIS camera show markings appearing on the nucleus of Comet 67P in recent months.
The scientist says that heating from the sun plays a major role in driving the changes, but apart from this, the story is more complex. A sequence of images taken by Rosetta's OSIRIS camera from the month of May till July reveals fresh circular features on the larger lobe of the Comet 67P/Churyumov-Gerasimenko. Large boulders and smooth plains are also seen that maybe covered with granular deposits.
According to Spaceflight Now, the region near comet 67P equator called Imhotep sees prolonged sunlight during each 12.4-hour rotation. Astronomers say that since August 2014 and till May 2015 no changes were noticed but suddenly first evidence for a new feature in the Imhotep region was captured on June 3. By June 13 second marking evidence was captured.
The significant growth on the comet measures 4.1 kilometers. A third marking appeared on July 2 and later more such pieces of evidence came up. Scientist predicted that the comet would shed materials during perihelion. Rosetta has also found evidence of erosion from previously occurred perihelion passage on the comet. Thus the changes observed on Imhotep are astonishing and unique to the comet. Thus scientist says registering changes on Comet 67P /Churyumov-Gerasimenko remains a key scientific objective for all Rosetta instruments to better understand how comets work and evolve.