Retrograde 'Trojan in Retreat' asteroid is one-in-a-million
Meteorologist/Science Writer
Tuesday, April 11, 2017, 6:52 PM - A one-in-a-million asteroid buzzes the planet Jupiter while going the "wrong way" around the Sun, and Thursday's planned NASA teleconference hints at something exciting about the icy moons in our solar system! It's What's Up In Space!
Astronomers find 'Trojan in Retreat'
There are a lot of asteroids flying around in our solar system - around a million or so that we know about - and a team of Canadian and American astronomers have discovered one that appears unique among them. Truly one in a million.
2015 BZ509 is what's known as a retrograde asteroid, meaning that it orbits around the Sun opposite to nearly everything else in the solar system. That is, while the planets and most other objects travel in a counter-clockwise direction around the Sun (when our solar system is viewed from "above"), this asteroid flies around in a clockwise direction.
"If you imagine the solar system as a racetrack, the planets are these monster trucks and Jupiter is the biggest monster truck of them all," says astronomer Paul Wiegert of the Department of Physics and Astronomy, and the Centre for Planetary Science and Exploration, at the University of Western Ontario. "Asteroids are like these ridiculously small clown cars going around the sun, all going in one direction … except for Bee-Zed."
There are roughly 80 or so other asteroids that do this same thing, however what makes Bee-Zed (as this asteroid is nicknamed) unique is that it occupies the same orbit of a planet while it does so. All of the other known retrograde asteroids orbit far from planets.
While the orbit of Bee-Zed is a simple tilted, skewed ellipse when you view it from an independent position in the solar system (see the video, above), it follows a much more interesting path if you're watching from Jupiter.
Weigert led the research into Bee-Zed, working with Martin Connors, from the Department of Physics and Astronomy at the University of Calgary and Athabasca University Observatories, and Christian Veillet, an astronomer at the Large Binocular Telescope Observatory, in Tucson, Arizona. Their findings appeared in the research journal Nature on March 29.
Weigert speaks about the asteroid and their research, below:
So, as Bee-Zed travels around the Sun, going "against the traffic," it does so in the same orbital region as Jupiter. That means that it not only zips through the two large clusters of asteroids that precede and follow Jupiter - the Trojans - but it also dodges the biggest planet in the solar system! Based on their research, Weigert, Connors and Veillet believe that Bee-Zed has been travelling along this tilted orbital path for more than a million years! Bee-Zed is a true daredevil!
Given its wrong-way orbit past Jupiter and through those Trojan asteroids, Martin Connors says that he calls it a "Trojan in Retreat."
Now, although Bee-Zed is referred to as an asteroid right now, in an email to The Weather Network, Connors said that the most likely explanation for Bee-Zed is that it is a comet. This is due to its size, since it is a few kilometres wide, and because many comets have retrograde orbits. Comet Halley is one famous example.
Things are never quite that simple, though. If Bee-Zed is a comet, he added, they aren't exactly sure how it got into this stable, retrograde co-orbit with Jupiter. There may be other retrograde comets, but none of them exhibit this weird behaviour. More observations and study of this object will undoubtedly provide more clues as to its nature and origin, and it could help scientists explain what's going on with other "weird" objects they discover, going forward.
"If there are objects doing weird stuff, it has to be for a reason," Connors said. "We are entering a new era of powerful sky scanning, and we will find weird stuff. Explaining how it all fits into the big picture is the hard part!"
Could it be aliens this time?
UPDATE! It turns out my speculations were correct! Read on, but then check out the latest on this here.
Alright, it's never been about aliens so far, and the chance of it being about aliens this time is probably pretty slim, but this is at least promising...
On Thursday, April 13, NASA is holding a teleconference on "Oceans Beyond Earth."
While this could be about any object space that could harbour a liquid water ocean - a moon of Jupiter or Saturn, or maybe Pluto or a planet orbiting another star - the list of speakers that will be in attendance would appear to narrow down the list of choices.
• Jim Green, the director of NASA's Planetary Science Division
• Mary Voytek, the Senior Scientist for Astrobiology in NASA's Science Mission Directorate
• Linda Spilker, the Cassini project scientist at NASA’s Jet Propulsion Laboratory
• Hunter Waite, the Cassini Ion and Neutral Mass Spectrometer (INMS) team lead at the Southwest Research Institute (SwRI)
• Chris Glein, a Cassini INMS team associate at SwRI
• William Sparks, an astronomer with the Space Telescope Science Institute, which operates the Hubble Space Telescope
What does that say? That this teleconference is likely about Saturn's icy moon, Enceladus, and also quite possibly Jupiter's icy moon, Europa.
Saturn's Enceladus (left) and Jupiter's Europa (right). The two are not to scale. Image Credits: Cassini Imaging Team/SSI/JPL/ESA/NASA and NASA/JPL-Caltech/SETI Institute. Composite by S. Sutherland
Enceladus is Saturn's sixth largest moon, and while it's only around 500 km across, its bright, ice-encrusted surface reflects back almost all the sunlight that falls on it, making it one of the brightest objects in our solar system. By comparison, Earth's Moon - as bright as it may be on some nights - only reflects back an average of about 13 per cent of the sunlight that falls on it. Scientists with the Cassini mission have been investigating plumes of water vapour streaming away from Enceladus' south polar region, which have hinted at the presence of an ocean of liquid water under the moon's icy crust. Further research has shown that it is a global ocean, and one that could be quite deep, with a crust of ice only around 20 kilometres thick in most places and down to just 5 km thick at the south pole. With such a large ocean under the surface, and having detected chemicals such as methane, carbon and complex organic molecules mixed in with the water vapour streaming away from the surface, Enceladus is one of the best places for us to find the very first hints of life beyond Earth.
Europa is the smallest of Jupiter's four Galilean moons, with an icy surface very much like Enceladus', but this moon is much larger, with a diameter of over 3,000 km. It was speculated that Europa could harbour alien life long before scientists considered Enceladus, and over the past five years, the Hubble Space Telescope has gathered evidence of water vapour plumes coming off of its surface, as well. NASA just recently committed to a specific mission to investigate this moon, called the Europa Clipper, which is expected to launch sometime in the 2020s.
But why these two? Simply due to the scientists who are involved in the teleconference.
Mary Voytek has been studying life in extreme environments for years, including in sub-glacial environments and around hydrothermal vents in the ocean - both relevant to these subsurface extraterrestrial oceans.
Linda Spilker has been with the Cassini mission for years, she has been involved in planning the spacecrafts investigations of Enceladus' plumes since their discovery, and she and Hunter Waite were among a group of researchers that presented an idea at the 46th Lunar and Planetary Science Conference, in 2015, for the Enceladus Life Finder - a spacecraft that could be sent to orbit Saturn and specifically aim its investigations at these plumes.
Just last year, Waite and Chris Glein (along with a colleague) published a paper about the pH (acidity or alkalinity) of Enceladus' ocean. Waite has also published research about methane in Enceladus' plumes.
Finally, when NASA announced even more evidence of plumes of water vapour streaming from Jupiter's moon, Europa, William Sparks was the one leading the team that found that evidence, using the Hubble Space Telescope.
Hubble apparently hasn't observed Enceladus' plumes before (the moon is likely too small and too distant), so that makes it more likely they'll be speaking about both moons (also the reference to "Oceans," rather than just "Ocean"). However, there is the possibility that Hubble was used to examine Saturn's E ring, which is a very diffuse ring of icy particles that shares Enceladus' orbit (and, in fact, comes from Enceladus), so that could simply narrow it down to only the one moon.
We'll just have to tune in to NASA TV, at 2 p.m. ET on Thursday, to find out!
Sources: Western University | Nature | NASA
