In September 2016, the European Space Agency’s (ESA) Rosetta spacecraft crashed into Comet 67P, bringing an end to 12 years of service — or so the ESA thought. While they believed they had already received Rosetta’s final image of the comet, the organization recently discovered one more, revealing the true final moment before impact.
The image previously thought to be Rosetta’s last was taken from a height of about 23.3 to 26.2 meters (76 to 86 feet), but the ESA estimates that this new image was taken from about 18 to 21 meters (59 to 68 feet) above the comet’s surface. They claim it captures an area of about one square meter (10 square feet).
When Rosetta purposefully set itself on a crash course with 67P, it transmitted the last of its images in six separate packets. However, due to an unexpected transmission interruption, only three made it back to Earth.
“Later, we found a few telemetry packets on our server and thought, wow, that could be another image,” said Holger Sierks, principal investigator for the OSIRIS camera at the Max Planck Institute for Solar System Research in Göttingen, Germany, in a statement.
The craft transmits images in layers, with each new layer adding detail to the image, so Sierks and his team had to assemble Rosetta’s final image one layer at a time. The ESA notes that while some of the finer details were lost, the final result is a zoomed-in shot of the spot Rosetta is thought to have impacted.
This may be the last we see from Rosetta, but it’s a fittingly unexpected end for a spacecraft that contributed so much to space exploration while traversing our solar system for more than a decade.
A future in which an asteroid crashes into Earth and destroys the planet — or all life on it, in the case of the dinosaurs — is prevalent in popular culture: Bruce Willis sacrificed himself to stop in happening in Armageddon, aliens have arrived on one in Day of the Triffids, and there have been a multitude of apocalyptic predictions on the news over the last few years. So, what is the precise nature of asteroids, and how likely are they wipe us from the face of the planet?
Asteroids are rocky bodies orbiting the Sun, which differ from comets in that they are composed of metal and rock rather ice, dust, and rock. They were formed 4.5 billion years ago, but don’t have sufficient gravity to round out like planets or have atmospheres.
Several asteroids have played pivotal roles in the world’s formation and cosmic history. An asteroid the size of Mars, which has been retrospectively named Theia, hit the Earth and was partially absorbed: some debris from the impact, though, was conglomerated by gravity to form the Moon. The most famous asteroid, though, is Chicxulub — the asteroid that wiped out the dinosaurs by causing sufficient sulphur displacement to block out the Sun.
Small asteroids hit Earth frequently, but rarely have any effect — the most violent example in recent memory was the 17- to 20-meter diameter Chelyabinsk meteor which hit Russia in February 2013, smashing windows and injuring 1,400 people in the process. Asteroids with a one-kilometer diameter hit Earth every 500,000 years or so; with the last known example of one with a 10-kilometer diameter occurring 66 million years ago. The chances of an asteroid apocalypse, then, are minimal.
There certainly is a risk from asteroid impacts; it’s the only natural risk that we as a species have the ability to predict well in advance and mitigate against, entirely, […] But I want people to keep it in context. You shouldn’t be losing sleep over it.
Our Plan to Avoid Destruction
Despite the chances of an asteroid apocalypse being fortunately slim, our planet has measures in place to protect against smaller near Earth objects (NEOs) like the Chelyabinsk meteor.
The main agency responsible for tracking and putting contingency measures in place is NASA’s Center for Near Earth Object Studies, which has a database sophisticated enough for us “to know within the next couple of decades for sure if any time over the next century if there’s an asteroid that’s going to hit,” Brown said in the interview. The organization, according to its 2016 report, is also developing “Methods for NEO Deflection and Disruption.”
NASA has already launched a progenitor for how a gravity-based asteroid diversion could work in the form of its Dawn Aircraft, which is currently orbiting the space rock Vesta. A future version of Dawn could exert a subtle gravitational pull on a space object, which would allow it to change the trajectory of rocks with remarkable subtlety and specificity. Rusty Schweickart, chairman of the B612 Foundation, who’s mission is to protect the world from asteroid attacks, said in an interview with Space.com, “you can get a very precise change in the orbit for the final part of the deflection using a technology of this kind.”
At the more futurist end of our planetary defense arsenal is the idea of “Mirror Bees.” Hypothetically, we could send a swarm of robotic spacecraft bearing mirrors to an asteroid, which would then focus the solar energy on one spot: Bill Nye, executive director of the Planetary Society, said to Space.com that “The reaction of that gas or material being ejected from the asteroid would nudge it off-course.”
While the threat of a dinosaur-level disaster is extremely slim, even small asteroids can still cause huge amounts of damage, destruction, and pain. It’s comforting that individuals and organizations are working towards developing methods to minimize the disruption asteroids — big or small — can cause.
In 1977, the sound of extraterrestrials was heard by human ears for the first time — or so people at the time thought. The Wow! Signal was detected by astronomer Jerry Ehman using Ohio State University’s Big Ear radio telescope. It is a radio signal detector that, at the time, was pointed at a group of stars called Chi Sagittarii in the constellation Sagittarius.
When scanning the skies around the stars, Ehman captured a 72 second burst of radio waves: He circled the reading and wrote “Wow!: next to it, hence the signal’s name. Over the last 40 years, the signal has been cited as evidence that we are not alone in the galaxy. Experts and laypeople alike believed that, finally, we had evidence of alien life.
These comets, known as 266P/Christensen and 335P/Gibbs, have clouds of hydrogen gas millions of kilometers in diameter surrounding them. The Wow! Signal was detected at 1420MHz, which is the radio frequency hydrogen naturally emits. Notably, the team has verified that the comets were within the vicinity at the time, and they report that the radio signals from 266/P Christensen matched those from the Wow! signal.
Other Extraterrestrial Communications
While this discovery is a disappointment to alien enthusiasts everywhere, as the Wow! Signal is the strongest signal we have ever received from space, it is a testament to our ability to accurately interpret signals and sounds from the cosmos. This gives us hope in our attempt to decode the hundreds of “strange, alien” signals coming from other stars that have been observed recently.
We have several weapons in our cosmic detection arsenal, most of which are used by the Search for Extra-Terrestrial Intelligence Institute (SETI). Their main means of detection is using radio-telescopes, and their most ambitious project to date has been ‘Project Phoenix’; the “world’s most sensitive and comprehensive search for extraterrestrial intelligence.”
For this project, they used three of world’s biggest radio telescopes: the Parkes radio telescope in Australia (210 feet in diameter), the National Radio Astronomy Observatory in West Virginia (140 feet in diameter), and Arecibo Observatory in Puerto Rico (the world’s largest at 1,000 feet in diameter). They have also built The Allen Telescope Array with financial backing from Paul Allen.
While the technology for detecting alien messages is remaining relatively static, ideas for communicating better with our own satellites is advancing rapidly, with possibilities including communicating by a laser beam and establishing a space satellite network.
In 2013, a meteor broke apart over Russia, sparking panic and injuring over 1,400 people. Called the “Chelyabinsk Event,” the culprit meteor was estimated to be around 17-20 m (56-65 ft) in diameter and released approximately 500 kilotons of energy. In fact, before the atmosphere absorbed most of the energy, the meteor had about 29 times the energy of the atomic bomb blast at Hiroshima.
Possible Asteroid Impacts
Every year, there could be dozens (if not more) of interstellar objects like comets and asteroids that come very close to Earth. In fact, as of January 3 of this year, 15,420 Near-Earth Objects(NEOs) had been discovered. On March 21, 2016, an NEO under 1 LD (lunar distance) from Earth was estimated to be 35-86 m (114.8-282.1 ft) in diameter. If that object had broken through the atmosphere and landed on Earth, the damage and devastation would be immense.
Yet even more threatening is the possibility of asteroid 2013 TV135 impacting the Earth. This asteroid has only a 1 in 63,000 chance of impacting within the next 100 years, but if it does, it would be absolutely catastrophic. The asteroid measures in at about 400 m (1,300 ft), which is around 4% of the size of the asteroid that is said to have killed the dinosaurs. So, while no dino-killer, the asteroid would certainly pack enough of a wallop to give the Earth one cosmic migraine.
The United States government is not taking the possibility of an asteroid impact lightly. In January of 2016, NASA joined with US defense and research agencies to form the Detecting and Mitigating the Impact of Earth-bound NEOs (DAMIEN) group. This group released a report detailing its strategy for dealing with NEOs.
The authors of this report state that “While it is highly unlikely that there will be a civilization-ending NEO impact over the next two centuries, the risk of smaller but still catastrophic NEO impacts is real…There is currently no whole-of government or international strategy to respond to such an even through all phases of a NEO impact scenario.”
Within the report, this group outlines seven strategic goals that they will use to help mitigate the risks of a possible asteroid impact.
1. Enhance NEO Detection, Tracking, and Characterization Capabilities
2. Develop Methods for NEO Deflection and Disruption
3. Improve Modeling, Predictions, and Information Integration
4. Develop Emergency Procedures for NEO Impact Scenarios
5. Establish NEO Impact Response and Recovery Procedures
6. Leverage and Support International Cooperation
7. Establish Coordination and Communications Protocols and Thresholds for Taking Action
According to Lindley Johnson, NASA’s Planetary Defense Officer: “The amount of time needed to mount a robotic planetary mission is typically 5-6 years, so I’d say realistically, you’d need about 8-10 years advance warning to do something about an asteroid in space.”
Our civilization is now truly global in scale and scope, and it behooves us to comport ourselves accordingly and take cognizance of all the potential threats to our survival—whether destructive wars, disease pandemics, climatic change, or the threat of extraterrestrial impactors. Hopefully, the survival of humanity will not be threatened by the impact of an NEO anytime soon; but if it is, we can rest a little easier knowing that measures are being taken and there is finally a sound plan in place.
Last October, NASA’s NEOWISE mission discovered a new comet whose aeons-long journey toward the Sun will swing it safely near the Earth in the opening days of 2017. It’s scheduled to zoom by us between now and January 14—when it’s expected to be so bright that it can be seen using just a pair of binoculars or even with the naked eye (caveat: cometary brilliance is infamously difficult to predict, e.g. the whole “ISON flop” of 2013).
This hyperbolic comet has been given the thoroughly unimaginative moniker of C/2016 U1 NEOWISE, and it “has a good chance of becoming visible through a good pair of binoculars, although we can’t be sure because a comet’s brightness is notoriously unpredictable,” Paul Chodas, manager of NASA’s Centre for Near-Earth Object (NEO) Studies, said.
It has already made its closest pass to the Earth, at a distance of about 106 million km (66 million miles), on December 13. By today, it’s around 140 million km (87 million miles) away. So there’s no need to worry. It’s not going to end life on Earth, or crash into anyone’s backyard.
Besides, researchers believe that C/2016 U1 NEOWISE’s orbit around the Sun takes millions of years, which means it’s probably the first time it’s visited the Earth. So enjoy the spectacle—it’s quite literally a once-in-a-lifetime event.
“At its brightest, comet C/2016 U1 NEOWISE will pass through the constellations Ophiuchus to Serpens Cauda and Sagittarius, and is best visible in the dawn sky 12 degrees from the Sun at maximum brightness,” according to Universe Today. Next week, it’ll be best viewed from the Northern Hemisphere just before dawn by looking toward the southeast.
Other Visitors to Speak Of
“NEOWISE is the asteroid-and-comet-hunting portion of the Wide-Field Infrared Survey Explorer (WISE) mission,” according to NASA. As such, C/2016 U1 NEOWISE isn’t the only object that it’s spotted recently. Another interesting discovery is a mysterious object that’s bound to pass by our skies in the coming weeks.
It’s been named 2016 WF9, and it’s not quite clear yet whether it’s a comet or an asteroid. “2016 WF9 could have cometary origins,” said James “Gerbs” Bauer at NASA JPL. “This object illustrates that the boundary between asteroids and comets is a blurry one; perhaps over time this object has lost the majority of the volatiles that linger on or just under its surface.” In other words, it might be a naked comet. It’s also relatively large—between 0.5 to 1 km (0.3 to 0.6 mile) across, and with a fairly dark surface that only reflects a few percent of the light that reaches it.
Regardless of what’s coming our way, 2017 is already shaping up to be a good year for night-sky gazing.