The meteor explosion over Russia in February 2013 raised concerns that even small asteroid impactors may wreak some havoc given our heavily populated cities. A new study by NASA scientists aims to improve our understanding of such asteroids that are lurking in Earth’s vicinity. The team, led by Amy Mainzer, noted that only a mere fraction of asteroids comparable in size to the object that exploded over Russia have been discovered, and their physical properties are poorly characterized.
The team derived fundamental properties for over a hundred near-Earth objects, and determined that many are smaller than 100 meters. Indeed, the team notes that, “In general … [asteroids] smaller than 100-m are only detected when they are quite close … and the smallest … were detected when they were only 2-3 lunar distances away from Earth.”
Essentially, a large fraction of these bodies may go undetected until they strike Earth, analogous to the case of the asteroid that exploded over Russia in February.
The team’s results rely partly on observations from the Wide-field Infrared Survey Explorer (WISE), which is a space-based telescope that mapped the entire sky in the mid-infrared. Observations taken in the infrared, in concert with those taken in the optical, can be used to infer the fundamental properties of asteroids (e.g., their diameter and chemical composition).
On a somewhat positive note, Mainzer remarks that 90% of near-Earth asteroids larger than 1-km are known, and those potential impactors are most worrisome as they may cause widespread fatalities. The dinosaurs suffered a mass-extinction owing, at least in large part, to a 10-km impactor that struck Earth 65 million years ago. However, Mainzer notes that the survey completeness drops to 25% for nearby 100-m asteroids, and it is likely to be less than 1% for 20-m asteroids like that which exploded over Russia (Chelyabinsk). The Tunguska event (see the image below) is likewise speculated to have been on the order of that latter size.
The team highlights that approximately 10,000 near-Earth objects have been discovered to date, 900 of which are 1-km or larger, and 3500 objects appear to be 100-m or smaller. “Because their small sizes usually make them undetectable until they are very nearby the Earth, it is often difficult for the current suite of asteroid surveys and follow-up telescopes to track them for very long.
Consequently, the fraction of the total population at small sizes that has been discovered to date remains very low,” noted Mainzer.
In closing, Mainzer emphasizes that, “It is, however, clear that much work remains to be done to discover and characterize the population of very small NEOs [near-Earth objects].”
The Mainzer et al. 2013 findings have been accepted for publication in the Astrophysical Journal (ApJ), and a preprint is available on arXiv. Coauthors on the study are J. Bauer, T. Grav, J. Masiero, R. M. Cutri, E. L. Wright, C. R. Nugent, R. Stevenson, E. Clyne, G. Cukrov, and F. Masci.
This question comes from Andrew Bumford and Steven Stormont.
In a previous episode I’ve talked about how the entire Solar System collapsed down from a cloud of hydrogen and helium left over from the Big Bang. And yet, we stand here on planet Earth, with all its water. So, how did that H20 get to our planet? The hydrogen came from the solar nebula, but where did the oxygen come from?
Here’s the amazing part.
The oxygen came from stars that lived and died before our Sun was even born. When those stars puffed out their final breaths of oxygen, carbon and other “metals”, they seeded new nebulae with the raw material for new worlds. We owe our very existence to the dead stars that came before.
When our Sun dies, it’ll give up some of its heavier elements to the next generation of stars. So, mix hydrogen together with this donated oxygen, and you’ll get H20. It doesn’t take any special process or encouragement, when those two elements come together, water is the result.
But how did it get from being spread across the early Solar System to concentrating here on Earth, and filling up our oceans, lakes and rivers? The exact mechanism is a mystery. Astronomers don’t know for sure, but there are a few theories:
Idea #1: impacts. Take a look at the craters on the Moon and you’ll see that the Solar System was a busy place, long ago. Approximately 3.8 to 4.1 billion years ago was the Late Heavy Bombardment period, when the entire inner Solar System was pummeled by asteroids. The surfaces of the planets and their moons were heated to molten slag because of the non-stop impacts. These impactors could have been comets or asteroids.
Comets are 80% water, and would deliver vast amounts of water to Earth, but they’re also volatile, and would have a difficult time surviving the harsh radiation of the young Sun. Asteroids have a lower ratio of water, but they could protect that water a little better, delivering less with each catastrophic impact.
Astronomers have also found many hybrid objects which contain large amounts of both rock and water. It’s hard to classify them either way.
Idea #2 is that large amounts of water just came directly from the solar nebula. As we orbited around the young Sun, it passed through the water-rich material in the nebula and scooped it up. Gravitational interactions between the planets would have transferred material around the Solar System, and it would have added to the Earth’s volume of water over hundreds of millions of years.
Of course, it’s entirely possible that the answer is “all of the above”. Asteroids and comets and the early solar nebula all delivered water to the Earth. Where did the Earth’s water come from? Astronomers don’t know for sure. But I’m sure glad the water is here; life here wouldn’t exist without it.
Is it Friday already? Then it’s time for another Weekly Space Hangout. Join a team of dedicated space journalists to discuss the big space and astronomy news stories that broke this week. This time around, we discussed Amy Shira Teitel’s Buran article, ISON Watch 2013, and the re-re-discovery of water on Mars.
We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern, 2000 GMT. You can watch from here on Universe Today, or over on Google+ or YouTube.
Once again, we have gathered together the forces of space journalism to report on the big news stories of the week. And there were lots of big stories indeed, with the launch of NASA’s LADEE mission to the Moon, and the awesome fact that Voyager 1 has totally left the Solar System.
Host: Fraser Cain
Journalists: Amy Shira Teitel, Nicole Gugliucci, Matthew Francis, David Dickinson, Nancy Atkinson
We record the Weekly Space Hangout every Friday at 12 pm Pacific / 3 pm Eastern as a live Google+ Hangout on Air. You can watch the show from right here on Universe Today, or on our YouTube channel.
This week offers a fine chance to catch sight of a unique asteroid.
324 Bamberga reaches opposition this week in the constellation Pisces on (friggatriskaidekaphobics take note) Friday the 13th at 7AM EDT/11:00 Universal Time.
About 230 kilometres in size, 324 Bamberga reaches 0.81 astronomical units from the Earth this week. No other asteroid so large gets so close.
Discovered on February 25th, 1892 by Johann Palisa, 324 Bamberga only reaches a favorable opposition once every 22 years.
Shining at magnitude +8.1, 324 Bamberga is also one of the highest numbered asteroids visible with binoculars. Earth-crossing asteroids 433 Eros, which made a close pass last year, and 4179 Toutatis are two of the very few asteroids that possess a larger number designations that can regularly reach +10th magnitude.
So, why did it take so long for 324 Bamberga to be uncovered? One factor is its high orbital eccentricity of 0.34. This means that most of the oppositions of the asteroid aren’t favorable. 324 Bamberga orbits the Sun once every 4.395 years and only comes around to an opposition that lands near perihelion once every 22 Earth years. Perihelion this year occurs only 45 days after opposition on October 27th.
The resonance between 324 Bamberga and Earth is nearly five Earth orbits for every one circuit of the Sun for the asteroid and is offset by only 9 days, meaning that the 22 year window to see the asteroid will actually become less favorable in centuries to come. 324 Bamberga made its last favorable appearance on September 15th, 1991 and won’t surpass +10th magnitude again until September 2035.
Observing asteroids requires patience and the ability to pick out a slowly moving object amidst the starry background. 324 Bamberga spends September west of the circlet of Pisces, drifting two degrees a week, or just over 17’ a day, to cross over into the constellation Pegasus in early October.
324 Bamberga will be moving too slow to pick up any motion in real time, but you can spy it by either sketching the field on successive nights or photographing the region and noting if the asteroid can be seen changing position against the background of fixed stars. Start hunting for 324 Bamberga tonight, as the Full Harvest Moon will be visiting Pisces later next week on the 19th.
324 Bamberga is also unique as the brightest C-type asteroid that is ever visible from Earth. The runner up in this category is asteroid 10 Hygiea, which can shine a full magnitude fainter at opposition.
It’s also remarkable that Palisa actually managed to discover 324 Bamberga while it was at 12th magnitude! Palisa was one of the most prolific visual hunters of asteroids ever, discovering 121 asteroids from 1874 to 1923. He accomplished this feat first with the use of a 6” refractor while based at the Austrian Naval Observatory in Pola (now the Croatian town of Pula) and later using the Vienna observatory’s 27” inch refractor.
324 Bamberga itself takes its name from the town of Bamberg in Bavaria, the site of the 1896 meeting of the Astronomische Gesellschraft.
An occultation of a star by 324 Bamberga on December 8th, 1987 allowed astronomers to pin down its approximate size. Searches have also been carried out during occultations for any possible moons of this asteroid, though thus far, none have been discovered.
It’s interesting to note that 324 Bamberga will also actually occult the star 2UCAC 3361042 tonight in the early morning hours at 8:59-9:10 UT for observers spanning a path from Florida to Oregon. The magnitude drop will, however, be very slight, as the star is actually 3 full magnitudes fainter than the asteroid itself. Dave Gee caught a fine occultation of a 7.4 magnitude star in the constellation Corvus by 324 Bamberga in 2007.
There’s also something special about this time of year and the region that 324 Bamberga is crossing. More visual discoveries of asteroids have been historically made in the month of September than any other calendar month. In fact, 344 of the first 1,940 numbered asteroids were found in September, more than twice the average. Palisa’s own track record bears this out, though 324 Bamberga was discovered in February.
One of the primary reasons for a September surge in discoveries is viewing direction. Astronomers of yore typically hunted for asteroids approaching opposition in the anti-sunward direction, which in September lies in the relatively star poor fields of Pisces. In December and June —the months with the lowest numbers of visual discoveries at only 75 and 65 for the “first 1,940” respectively —the anti-sunward point lies in the star-rich regions of Sagittarius and Gemini. And by the way, the meteor that exploded over the city of Chelyabinsk on February 15th was sneaking up on the Earth from the sunward direction.
Be sure to catch a glimpse of this unique asteroid through either binoculars or a telescope over the coming weeks. The next chance to observe 324 Bamberga won’t roll around again until September 2035… it’ll be great to compare notes of the 2013 apparition on that far off date!
NASA is really getting into this crowd-sourcing thing. The space agency asked and the public responded with hundreds of ideas of what missions could be done with asteroids in regards to protecting Earth from these space rocks and finding an asteroid humans can explore. NASA received over 400 responses to their “Asteroid Initiative Request For Information” request, hearing from the space industry, universities, and the general public.
Now, after looking at all the responses, NASA has chosen 96 ideas it regards as most promising, ranging from asteroid observation plans to asteroid redirection, deflection or capture systems, to creating crowd sourcing and citizen science opportunities.
Next, NASA will host an Asteroid Initiative Idea Synthesis Workshop where NASA personnel and the space community will discuss and further these 96 ideas to narrow them down even further to help with its planning activities and future missions.
The 96 ideas were chosen by a team of NASA scientists, engineers, and mission planners who evaluated the proposed ideas. The evaluation team rated the responses for relevance to the RFI objectives, innovativeness of the idea, maturity of the development approach, and potential to improve mission affordability.
This is the first time NASA has used this type of crowd-sourcing and discussion method to look at possible future missions.
NASA said the ideas proposed “provide the agency with fresh insight into how best to identify, capture and relocate a near-Earth asteroid for closer study and respond to asteroid threats.” Ideas included pointers on how to decrease an asteroid’s spin, nudge it away from a path toward Earth, take samples to return to Earth and create activities to heighten public awareness of not only the threat asteroids pose, but the valuable resources and scientific benefits they may offer.
“This rich set of innovative ideas gathered from all over the world provides us with a great deal of information to factor into our plans moving forward,” said Robert Lightfoot, Associate Administrator for NASA. “We’re making great progress on formulating this mission, and we look forward to discussing further the responses we received to the RFI.”
The upcoming public workshop will be held on Sept. 30 – Oct. 2 and onsite participation is limited to just the presenters, but it appears the workshop will be webcast (more info later), as NASA said they will release information on virtual participation options as the workshop nears.
NASA has released some new photos and video animations outlining the concept of how their planned asteroid capture mission will work. The plan is to find, capture, redirect a near-Earth asteroid to a stable point near the Moon in order to explore and study it. As we’ve said previously, it’s still unclear if NASA will receive Congressional funding or authorization to do an asteroid retrieval mission, but the agency is moving ahead with its planning work for now.
NASA recently did a mission formulation review to look at some internal studies on the mission, as well as taking a look at over 400 ideas the space community submitted concerning the mission.
The new images show crew operations including the Orion spacecraft’s trip to and rendezvous with the relocated asteroid, as well as astronauts maneuvering through a spacewalk to collect samples from the asteroid.
You can watch the video and see more images below.
NASA is also looking at new technologies like a Solar Electric Propulsion System is an essential part of future missions into deep space with larger payloads. The use of advanced SEP offers more mission flexibility, NASA said.
If you’d like to get involved or add your input, NASA will host a technical workshop at the Lunar and Planetary Institute in Houston from Sept. 30 to Oct. 2 to discuss potential ideas. Virtual participation will be available to the public, and when the details of how to participate become available, Universe Today will post an update.
A hibernating spacecraft has been called back into service. The WISE (Wide-field Infrared Survey Explorer”) spacecraft that has been sleeping in a polar orbit around Earth for two years will be turned back on next month to hunt for more potentially hazardous asteroids, and perhaps search for an asteroid that NASA could capture and explore in the future.
“The WISE mission achieved its mission’s goals and as NEOWISE extended the science even further in its survey of asteroids. NASA is now extending that record of success, which will enhance our ability to find potentially hazardous asteroids, and support the new asteroid initiative,” said John Grunsfeld, NASA’s associate administrator for science. “Reactivating WISE is an excellent example of how we are leveraging existing capabilities across the agency to achieve our goal.”
WISE originally was launched in December 2009 and scanned the entire celestial sky in infrared light about 1.5 times, searching for the coolest stars, the universe’s most luminous galaxies and some of the darkest near-Earth asteroids and comets. It captured more than 2.7 million images of objects in space, ranging from faraway galaxies to asteroids and comets close to Earth.
However, in early October 2010, after completing its prime science mission, the spacecraft ran out of the frozen coolant that keeps its instrumentation cold. But two of its four infrared cameras remained operational, which were still optimal for asteroid hunting, so NASA extended the NEOWISE portion of the WISE mission by four months, with the primary purpose of hunting for more asteroids and comets, and to finish one complete scan of the main asteroid belt.
The NEOWISE mission completed a full sweep of the main asteroid belt, and during 2010, NEOWISE observed about 158,000 rocky bodies out of approximately 600,000 known objects. Discoveries included 21 comets, more than 34,000 asteroids in the main belt between Mars and Jupiter, and 135 near-Earth objects.
“The data collected by NEOWISE two years ago have proven to be a gold mine for the discovery and characterization of the NEO population,” said Lindley Johnson, NASA’s NEOWISE program executive in Washington. “It is important that we accumulate as much of this type of data as possible while the WISE spacecraft remains a viable asset.”
Now WISE will again search for asteroids with a new extra-extended three year mission to search for more PHAs as well as suitable asteroids for future human exploration missions.
NASA said they anticipate WISE will use its 16-inch (40-centimeter) telescope and infrared cameras to discover about 150 previously unknown NEOs and characterize the size, albedo and thermal properties of about 2,000 others — including some of which could be candidates for the agency’s recently announced asteroid initiative.
“The team is ready and after a quick checkout, we’re going to hit the ground running,” said Amy Mainzer, NEOWISE principal investigator at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “NEOWISE not only gives us a better understanding of the asteroids and comets we study directly, but it will help us refine our concepts and mission operation plans for future, space-based near-Earth object cataloging missions.”
It’s time for another Weekly Space Hangout, where we give you a rundown of the big space news stories of the week, from a team of scientists and space journalists.
We record the Weekly Space Hangout live on Google+ every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch the show live here on Universe Today, or the archived version on YouTube.
It’s time for another Weekly Space Hangout, where a dedicated team of space journalists run down all the big stories in space and astronomy for the week of July 26, 2013.
We record the Weekly Space Hangout live as a Google+ Hangout on Air every Friday at Noon Pacific, 3:00 pm Eastern. You can watch the show live on Google+, or here on Universe Today. But you can also watch the archive after the fact, if live video isn’t your thing.