Buzz
The Rosetta Spacecraft stands as a true technological marvel. Launched and overseen by the European Space Agency (ESA), this brave probe embarked on the most extraordinary journey of any human-made object.
Philae’s successful landing on comet Churyumov-Gerasimenko marked the result of more than four decades of planning and a decade of precise, tense space travel. The spacecraft completed three orbits around Earth, made one pass by Mars, entered a 31-month hibernation, and eventually landed on a 4-kilometer-wide (2.5 mi) rock racing through space at speeds reaching up to 135,000 kilometers (83,000 mi) per hour. Superheroes are real, and they work at the ESA.
10. CG Captures Jupiter in Motion
Jupiter, a colossal planet, exerts a gravitational pull that affects the entire solar system. This massive gas giant continuously disrupts the orbits of comets, flinging them toward the Sun, out into the vastness of space, or sometimes even on a direct path toward Earth.
The Kuiper Belt, a vast region of icy rocks beyond Neptune, supplies Jupiter with plenty of ammunition. It is believed that Churyumov-Gerasimenko originated from this belt, making CG and similar comets part of the Jupiter Family comets. These comets have orbital periods of around 20 years (with CG’s period being 6.6 years), regularly venturing into the inner solar system, making them ideal candidates for exploration.
The abundance of comets in the solar system makes them somewhat interchangeable, and the current CG mission is actually a backup plan. Originally, Rosetta was slated to meet a different comet, 46/P Wirtanen, but delays in the program led to a change in plans as Wirtanen sped past.
While it's long been known that Jupiter has a knack for bullying smaller objects, the journey of comet CG has provided us with an unprecedented view of this phenomenon. Far from the Sun, CG remained frozen and invisible to us, but its trajectory was drastically altered by Jupiter's gravitational force, sending it dangerously close to the Sun. As it approaches perihelion in the coming months, CG will begin to evaporate.
9. The Comet Is Singing
Strange events are unfolding on Churyumov-Gerasimenko. As Rosetta drew closer to CG in August for its first encounter, its magnetometer detected a series of unusual sounds emanating from the comet. Beyond the range of human hearing, a set of instruments called the Rosetta Plasma Consortium recorded this dissonance at frequencies between 40–50 mHz.
Astronomers were pleasantly surprised by CG's unexpected melody, as they had not anticipated the comet producing any sounds. The exact cause remains unclear, but it seems to stem from magnetic interactions between the comet, gas, and the Sun.
First, the vaporized ice escaping from the comet is ionized by UV radiation from the Sun. This ionized cloud, now filled with charged particles, forms a barrier against the radioactive solar wind. The oscillations, driven by magnetic and electrical friction within the comet’s virtually nonexistent atmosphere, could be the source of the strange sounds recorded by Rosetta.
8. The Longest Jump Ever
Due to a partially unsuccessful landing and the weak gravity of tiny CG, the Philae lander achieved the longest, slowest jump ever. After failing to anchor itself after its initial touch, it bounced off the comet, nearly flying back into space, narrowly escaping a much harsher fate after its historic 10-year trek around the inner planets.
On a positive note, Philae managed to soar impressively, leaping up to 1 kilometer (0.6 mi) from the surface—about 25 percent of the comet’s total length. This was followed by a smaller bounce before the lander finally came to rest in a shadowed area at the base of a rocky ridge. Due to CG’s feeble gravity, Philae was caught in this unplanned transit for almost two hours before it finally settled down.
Despite what appeared to be a catastrophic mishap, Philae’s instruments were not significantly damaged, and the lander completed roughly 90 percent of its mission objectives. If anything, the unexpected jump turned out to be a hidden advantage.
Initially, astronomers observed a plume of dust kicked up by the impact, providing valuable data on the comet's surface composition.
Moreover, the jump may have played a crucial role in ensuring Philae’s long-term survival. Had it landed as planned and secured itself in the chosen spot, the constant exposure to sunlight could have damaged its circuits over time. Instead, by landing in the shadow, it may have enough solar energy to recharge as the comet moves closer to the Sun, potentially by spring 2015. With only the power equivalent to a few AA batteries needed to restart, there’s plenty of reason for optimism.
7. Massive Cliffs
CG boasts some massive cliffs. As previously mentioned, CG measures only a couple of miles in length and width, so the 1-kilometer-high (0.6 mi) cliff that Rosetta focused on is about a quarter of the size of the entire comet. For comparison, imagine mountain ranges on Earth extending thousands of miles into space, and keep in mind that Everest, at only 29 kilometers (5.5 mi) high, is relatively modest.
Amateur astronomer Stuart Atkinson noticed the stunning peaks while reviewing images from the ESA. He cropped one of the pictures to emphasize a sheer, dizzying cliff face that rivals any vibrant nebula in beauty. NASA took notice of Atkinson's work and awarded him the Astronomy Picture of the Day honor on December 23.
The original image is a composite of four separate shots taken from Rosetta’s NAVCAM, from a distance of 20 kilometers (12 mi). After zooming in and cropping, Atkinson highlighted the cliff in all its rugged splendor, its size accentuated by the contrast against the empty blackness of space.
The collection of boulders at the cliff’s base is equally striking. These rocks are massive in proportion, some measuring over 18 meters (60 ft) across, yet they're only weakly tethered by the comet's minimal gravity and are much lighter than they might seem. In fact, you could leap off that kilometer-high cliff and land safely at the bottom without so much as a sprained ankle.
6. It Looks Like A Duck
The reason why the comet resembles a rubber duck remains a mystery. It may sound unbelievable, but astronomers didn’t even know what CG looked like until just a month before they landed on it. Imagine the astonishment at mission control when they saw a blurry rubber duck staring back at them in July, when Rosetta finally got close enough to take some pictures of the peculiar-shaped comet.
Far more interesting than a simple, round comet, CG’s double-lobed shape has given astronomers much more to think about. How did it form? While the exact process is uncertain, there are several possibilities.
One theory suggests a low-speed, uneventful collision fused two comets together into one irregular super-comet. Alternatively, it’s possible that CG was once a rounder comet, but gravitational forces from a massive body like Jupiter deformed it. Another possibility is that CG started as a larger chunk of ice, but most of it was lost into space, leaving behind a strange core. Future research will hopefully shed light on whether CG is a single, deformed body or a collection of cosmic debris.
5. On The Origin Of Earth’s Water
Comet CG is thought to be a relic from the vast debris field that eventually formed the Sun, planets, and everything else in our solar system. As a result, it provides a chemical snapshot of the ancient past, and its components offer valuable insights into the composition of the early solar system.
CG also holds frozen water, which could help us solve the long-standing mystery of how water arrived on Earth. Using mass spectrometry, astronomers can examine celestial bodies to determine their chemical makeup, and many comets and asteroids have been studied in this way.
Hydrogen exists in various forms, including deuterium, a heavier isotope of hydrogen with an extra neutron. By studying the ratio between normal hydrogen and deuterium (the D/H ratio), astronomers can trace the origin of the water they’ve sampled.
The water found on comet CG doesn’t resemble the water on Earth. In fact, the same can be said for most other comets. Only 1 out of 11 comets studied had water that was similar to Earth’s. Interestingly, members of the asteroid belt have been found to contain Earth-like water, though in very small amounts. This implies that Jupiter Family Comets (and comets in general) are not responsible for Earth’s water content. It’s even possible that CG has a more unusual origin than we initially thought.
4. CG Smells Horrible
Space typically keeps our senses useless, so we don’t often think about what planets and comets might smell like. But thanks to Rosetta, we now know the answer to at least one of those questions. The spacecraft used its mass spectrometers as a sort of smelloscope to analyze the cloud of gases surrounding Churyumov-Gerasimenko’s nucleus.
Describing the scent of comet CG as that of garbage would actually be an understatement. The gases emitted by CG create a combination of nearly every fundamental stench known to man. Hydrogen sulfide gives off the smell of rotten eggs, while formaldehyde adds a death-like aroma. Methane and ammonia mix together to resemble the pungent odor of cat urine and horse dung. Sulfur dioxide contributes a vinegar-like tang, and a variety of other compounds blend in to complete the overall essence of filth.
The European Space Agency (ESA) was caught off guard by these findings. Given CG’s current distance from the Sun, it was expected that only carbon monoxide and carbon dioxide would be released, with everything else remaining frozen until the comet approaches perihelion. Aside from repelling our senses, CG’s scent profile (determined through spectral analysis) could also provide valuable insight into the comet’s origins.
3. It Imaged Two Asteroids As Well
During its decade-long voyage to comet Churyumov-Gerasimenko, the Rosetta spacecraft encountered a few cosmic wanderers. On September 5, 2008, it passed asteroid Steins and took a photo of the several-mile-wide rock. Steins bears the scars of ancient impacts, including a crater that takes up nearly half of its surface. The asteroid is so remarkably shiny that it’s often called “a diamond in the sky.”
On July 10, 2010, asteroid Lutetia (shown above) passed by the spacecraft at a distance of nearly 3,200 kilometers (2,000 mi). Measuring over 100 kilometers (60 mi) in diameter, Lutetia is covered in craters. The heavily scarred surface suggests that the asteroid is more than 3.4 billion years old and might be a leftover fragment from the formation of our solar system. Lutetia also displays hundreds of unusual grooves, similar to those seen on Mars's moon Phobos, as well as on two other asteroids.
2. Tougher Than We Thought
ESA’s Philae lander was designed to get hands-on with the comet. The exciting SD2 system is responsible for puncturing the comet's surface and sending samples to a series of onboard chemistry labs and over 20 ovens. With a drill that’s 100 times more efficient than a household model, it can drill up to 23 centimeters (9 inches) deep, aiming to collect a pristine sample of comet material.
Unfortunately, Philae’s landing didn’t go according to plan, and it ended up in a less than ideal position. The drilling operation was nearly abandoned due to Philae's precarious state. With one leg lifted awkwardly in the air like a dog marking a tree, activating the drill could have potentially worsened its position.
However, the drilling went ahead, and according to the German Aerospace Center (DLR), the comet proved to be “a tough nut to crack.” It’s still unclear whether the drill managed to retrieve a usable sample, but organic molecules were detected in the thin atmosphere of CG.
Despite the challenges, the operation yielded some surprising results, such as the unexpected toughness of the crust, as ESA had anticipated soft, fluffy ground. The comet was also found to have a substantial amount of water, with abundant ice locked inside, rather than a mixture of frozen gases.
1. The Surprising Color
Though Churyumov-Gerasimenko might look like a pale, dusty gray in many photos, that's merely an illusion. The above image is a “true color” rendering, presenting the comet in its reddish-brown hues. However, that too is a bit misleading, as CG wouldn't appear nearly as bright and colorful to an observer near it.
The reddish-brown shade would only be visible if the comet were lit by pure, white light. In reality, it’s more of a dark smudge against an even darker background of space, only becoming more visible as it approaches the Sun and develops a tail from the layers it sheds. At present, without a tail, the comet remains almost invisible.
However, recent images from OSIRIS, Rosetta's main imager, reveal the comet in its true monochrome splendor. These photos, which combined three shots taken through red, green, and blue filters, show CG as one of the grayest things we’ve ever seen, with nearly no variation in color on its surface. Much like other comets in its group, CG is incredibly dark—almost as black as coal, according to Holger Sierks, OSIRIS’s Principal Investigator.
Despite the wealth of data gathered on Churyumov-Gerasimenko, a substantial portion of it remains enigmatic. Although Rosetta arrived at the comet in August, its southern hemisphere remains unexplored and is likely to stay that way until the comet moves closer to the Sun. It may seem improbable, but the comet’s rotational axis is tilted relative to its orbit, causing the south pole to remain in constant darkness for months.
Rosetta has managed to capture an image of the comet’s shadowed side, but only through the backscattered light reflecting off the dust particles streaming away from the comet. The faint sunlight allows a glimpse of a small section of the comet’s dark side, though the details of the landscape remain indistinguishable. ESA considers this hidden side to be the most intriguing, as it has been significantly shaped by the comet’s activities.
