Abbreviation | DFN |
---|---|
Type | camera network |
Purpose | Record meteorite falls |
Headquarters | Perth |
Region served | Australia |
Affiliations | Curtin University |
Website | dfn |
The Desert Fireball Network (DFN) is a network of cameras in Australia. It is designed to track meteoroids entering the atmosphere, and aid in recovering meteorites. It currently operates 50 autonomous cameras, spread across Western and South Australia, including Nullarbor plain, WA wheatbelt, and South Australian desert, covering an area of 2.5 million km2. The locations of the stations were chosen to facilitate meteorite searching. Starting in 2018, cameras deployed across the world began the first global fireball observatory in association with partner research teams.
The DFN observatories capture approximately 30-second exposures of the sky from dusk until dawn every night, and the DFN team is automatically alerted if a fireball or meteor is detected. Based on the long-exposure images, trajectories and orbits are plotted in a semi-automated manner, and a fall-line is generated to indicate the whereabouts and mass of any resultant meteorites on the ground.
The DFN is advancing the knowledge base of the current understanding of planetary system formation and evolution. By connecting a specific meteorite with a fireball trajectory and orbit leading up to impact on Earth, scientists can obtain a better understanding of where meteorite samples came from in the Solar System. Once a likely region of origin in the main asteroid belt is identified, candidate parent bodies can be explored. [1] [2] [3]
When the meteorite is found and collected, a myriad of analyses can take place that shows what conditions were like on the parent body and what has happened to the rock over its lifetime. [4] This means a detailed compositional map of the Solar System can be built, which shows how asteroid and near-Earth objects vary in composition and can better inform Solar System evolution models and planetary science research. [2] [5]
The ultimate aim for this project is to find a cometary meteorite. [6] Comets are some of the most pristine materials in the Solar System, and contain a unique record of early Solar System processes. [7] There is growing evidence to suggest that cometary fireballs are delivering meteorites to Earth, and so the setup of this project is ideal to observe the fall and collect any cometary samples, which space agencies around the world have spent a huge sum of money to obtain through space missions. [1]
A number of teams have put together fireball observatories based on the same principles, e.g. the Prairie Network [8] (US) and the Canadian Meteorite Observation and Recovery Network, [9] which were led primarily by observational astronomers, and yet collectively have only determined orbits for four meteorites. [1]
The interest in this approach heightened in 2008 when a telescopic astronomical sky survey detected a meteoroid on an Earth-bound trajectory, and successfully pinpointed its location on the Earth's surface. A connection between the candidate asteroid type and the meteorite was made based on the object's composition and orbit, but such observatories only see a small portion of the sky, and so the likelihood of observing such events regularly is somewhat low.
Prior to this in 2007, the DFN was in its analogue trial phase in the Nullarbor desert plains of Western Australia. [1] As soon as the network was running, meteors were being observed, and on the first recovery trip, and on the very first day, the meteorite was found only 100 m from the predicted fall line. [5] [10] In part, the rapid success the DFN enjoyed relates to the location of the network- desert locations are far more favorable for recovery, as regions of dense vegetation, such as the temperate regions of the northern hemisphere, make meteorite recovery almost impossible. [1] Subsequent to the trial phase and recovery of two meteorites during this time, the DFN expanded into an automated digital fireball observatory, [11] [12] [2] [13] which is now expanding further to new regions of Australia and overseas. [14] [1] So far, four meteorites have been recovered with a high-accuracy trajectory and orbit defined. [1]
Meteorites are metallic or stony objects that fall to the Earth's surface from outer space. Scientists believe that most meteorites originate from asteroids within the asteroid belt of the Solar System, but there is an increasing amount of evidence to suggest some may come from comets. Some meteorites also come from larger planetary bodies, such as the Moon and Mars. [15] Meteorites typically preserve their histories from the time when they were first accreted on their parent body, to when they were ejected from that body and landed on Earth, so our understanding of planetary body formation and evolution over the last 4.56 billion years [16] becomes better each time a new meteorite is found.
The meteorite fall that is observed using the DFN observatory helps to inform how a body interacts with the Earth's atmosphere, how it decelerates, how bright the meteor is depending on the object, and the changes in mass whilst it falls due to ablation. [13]
A large number of analytical tests allow scientists to examine the meteorites and delve into their complex histories. The composition, texture and components of a meteorite help to identify the meteorite class it belongs to. Over time, the global meteorite collections have been used to identify groups of rocks with similar characteristics, which are presumed to originate from the same parent body, or same family of bodies. [17] Subtle differences within these groups hint at variations on the parent body- be those compositional or textural- which implies the suspected parent body may not be uniform, perhaps in a similar way to Earth. Iron meteorites are interpreted to be the core of large asteroids that may no longer exist in the Solar System. [18] They may once have been surrounded by a silicate shell on the parent body, [18] implying that other silicate-rich meteorites originated from the same parent body too, despite the clear compositional differences. This means the processes occurring deep within asteroids can be learned fairly easily, and knowledge about the composition of the inner core of Earth can be based on these rocks.
Highly primitive meteorites contain some of the first solids to have formed in the Solar System. These materials have been used to date a more precise age of the Solar System (4.568 billion years). These rocks are primitive because they have changed very little since their initial formation. [16]
Impact science also benefits from the delivery of meteorites. The Earth has been struck by large impacts in its past e.g. Chicxulub crater, and the materials left behind and the effect on the ground improves impact modeling predictions. The effects on Earth can also be used to understand similar patterns that have been observed on other planets, creating a wealth of understanding of impact cratering on different planets and planetary bodies. [16]
The DFN has recovered five meteorites with highly accurate trajectory and orbital data so far. [1] The two more recent recoveries, Murrili and Dingle Dell, were collected within a very short timeframe following the observed fall, [19] [20] meaning the digital progression of the network pipeline is becoming more and more effective as time progresses. [1] [2]
Meteorite name | Fall observation date | Country | State, province, or region | Classification | Instrumentally observed - orbital data | Meteoritical Bulletin(s), other references |
---|---|---|---|---|---|---|
Bunburra Rockhole | July 21, 2007 | Australia | South Australia | Brecciated achondrite | Yes | [21] [22] [10] |
Mason Gully | April 13, 2010 | Australia | Western Australia | H5 | Yes | [23] [24] [25] |
Murrili | November 27, 2015 | Australia | South Australia | H5 | Yes | [26] [27] |
Dingle Dell | October 31, 2016 | Australia | Western Australia | L/LL5 | Yes | [28] [20] |
Arpu Kuilpu | June 1, 2019 | Australia | South Australia | H5 | Yes | [29] [30] |
Puli Ilkaringguru | November 18, 2019 | Australia | Western Australia | H5 | Yes | [31] |
Madura Cave | June 19, 2020 | Australia | Western Australia | L5 | Yes | [32] [33] |
Kybo-Lintos | April 1, 2021 | Australia | Western Australia | H4/5 | Yes | [34] |
The DFN observatories use consumer still photographic cameras (specifically DSLRs) with 8mm stereographic fish-eye lenses covering nearly the entire sky from each station. The cameras are controlled via an embedded Linux PC using gPhoto2 and images are archived to multiple hard disk drives for storage until the observatories are visited for maintenance (every 8–18 months depending on the storage capacity). [35]
The observatories take one long exposure image every 30 seconds for the entire night. After capture, automated event detection searches the images for fireballs, and events are corroborated on the central server using images from multiple stations.
A GNSS synchronised time code is embedded in the long exposure images by the operation of a liquid crystal (LC) shutter to provide absolute timing data for fireball trajectories after triangulation with temporal precision better than one millisecond. [36] Absolute timing is used for the calculation of meteoroid orbits and the relative timing also embedded by the timecode is required for trajectory analysis (specifically to calculate the mass from the deceleration of the meteoroid).
The rate of data acquisition requires an automated digital pipeline for data reduction. A wireless link to each Automated Fireball Observatory allows a cross-check for multi station confirmation and enables images to be remotely downloaded. Software has been created to facilitate the location of fireball trajectories in pixel coordinates. These are converted to celestial coordinates, to a minute of arc precision, by using a powerful astrometric calibration tool created to automatically identify surrounding stars, and use them as a referencing system. The different observation angles are triangulated using a modified least squares minimisation approach, which now includes weightings based on image quality to produce the full observed trajectory . A shutter system within the lens of each observatory encodes a unique non-repeating De Bruijn sequence into each fireball. This provides accurate, absolute timing information for the duration of the trajectory to 0.4 ms. Purpose written software uses entry parameters to determine orbits for each meteoroid. In order to determine if there will be a potential meteorite, the estimation of the changing meteoroid mass is modeled. Once ablation stops, the atmospheric winds strongly affect a meteoroid's path to the ground. Data from the Global Forecasting System is used in an atmospheric wind model with a 0.008 degree resolution mesh uniquely created around the area of the fireball. A Monte Carlo dark flight simulation is performed to determine a likely search area for main mass and fragments.
The dark flight trajectory of a meteoroid is significantly affected by the atmospheric winds, especially by the jet stream. As a result, the meteorite fall position can be shifted by up to several kilometers compared to a scenario with no winds.
The weather situation in the area around the end of the luminous flight is numerically modeled using the third generation of Weather Research and Forecasting (WRF) model with dynamic solver ARW (Advanced Research WRF). The weather model is typically initialized using global one-degree-resolution National Centers for Environmental Prediction (NCEP) Final analysis (FNL) Operational Model Global Tropospheric Analysis data. The model produces 3D matrix for given area and time, with horizontal resolution down to 1 km. From this 3D data, weather profiles are extracted; the components include wind speed, wind direction, pressure, temperature and relative humidity at heights ranging up to about 30 km altitude, in most cases fully covering the dark flight.
The DFN produces hundreds of terabytes of data per year, which mostly consists of high resolution all-sky images. With the proposed network expansion, this volume is going to increase. For the primary purpose of this network, meteorite recovery, only a small fraction of this data (images containing fireballs) is needed, and it is handled by the data processing pipeline (above). However, there are many other potential uses for the data is areas of Astronomy or Space Situational Awareness.
The full data volumes recorded by the cameras are too large to be transferred remotely. Removable hard drives are therefore collected during regular servicing of the DFN observatory sites, replaced with blank hard drives, and then transported to Perth to be archived in a data store at the Pawsey Supercomputing centre. The multi-petabyte data store allows searching of the dataset, using generic and project-custom metadata, and data sharing with other research groups.
Meteorite fall predictions from a camera network typically produce a "fall line"—a straight or curved line on the ground typically a few km long—where it is believed the meteorite has fallen somewhere along the line, but its precise location is unknown. This is a result of the triangulation process, the effect of atmospheric winds during the fall, and knowledge of the apparent visible deceleration of the meteorite, but a lack of knowledge of its density, shape and precise mass.
Meteorite searching theory owes much to search and rescue theory, albeit somewhat simplified as the meteorite is not a moving target. Most of the falls observed by the DFN are in the remote outback, and so searching teams usually consist of 4-6 people, who camp on site for up to two weeks. This means that the searching strategy is focused on efficiency, rather than speed: meteorite recovery on the final day of the expedition is just as scientifically valuable as the first day, which contrasts to, for example, missing person search and rescue, where speed is of the essence. The practical searching techniques used by the DFN team are adapted to the predicted fall size and error ellipse:
Fireballs in the Sky is the award-winning outreach and citizen science program that shares the story of the desert fireball network. Fireballs in the Sky engages people of all ages, all over the world to share in this wonder of fireball and meteorite science. This innovative outreach program encourages global citizens to get involved in the research by reporting fireball sightings through the Fireballs in the Sky app, produced with ThoughtWorks. Through augmented reality, an intuitive interface and sensing technology of a smartphone app, anyone anywhere in the world can recreate their fireball sighting to contribute scientifically useful data. To download the app and see the latest reports from around the world, head to the app-sightings here. It is currently the best available system for reporting accurate public fireball sighting in the world, and feeds directly into the database of the DFN.
The DFN project is based at Curtin University in Perth, Western Australia. Together with NASA, the DFN is expanding to a Global Fireball Observatory through the Solar System Exploration Research Virtual Institute (SSERVI). SSERVI's science and technical research focuses on the connection between planetary exploration and human exploration via funded U.S. teams and a large network of international partners.
A meteorite is a rock that originated in outer space and has fallen to the surface of a planet or moon. When the original object enters the atmosphere, various factors such as friction, pressure, and chemical interactions with the atmospheric gases cause it to heat up and radiate energy. It then becomes a meteor and forms a fireball, also known as a shooting star; astronomers call the brightest examples "bolides". Once it settles on the larger body's surface, the meteor becomes a meteorite. Meteorites vary greatly in size. For geologists, a bolide is a meteorite large enough to create an impact crater.
A meteoroid is a small rocky or metallic body in outer space. Meteoroids are distinguished as objects significantly smaller than asteroids, ranging in size from grains to objects up to a meter wide. Objects smaller than meteoroids are classified as micrometeoroids or space dust. Many are fragments from comets or asteroids, whereas others are collision impact debris ejected from bodies such as the Moon or Mars.
An impact event is a collision between astronomical objects causing measurable effects. Impact events have been found to regularly occur in planetary systems, though the most frequent involve asteroids, comets or meteoroids and have minimal effect. When large objects impact terrestrial planets such as the Earth, there can be significant physical and biospheric consequences, as the impacting body is usually traveling at several kilometres a second, though atmospheres mitigate many surface impacts through atmospheric entry. Impact craters and structures are dominant landforms on many of the Solar System's solid objects and present the strongest empirical evidence for their frequency and scale.
Meteoritics is the science that deals with meteors, meteorites, and meteoroids. It is closely connected to cosmochemistry, mineralogy and geochemistry. A specialist who studies meteoritics is known as a meteoriticist.
The Tagish Lake meteorite fell at 16:43 UTC on 18 January 2000 in the Tagish Lake area in northwestern British Columbia, Canada.
Tooting is an impact crater with volcanic features at 23.1°N, 207.1°E, in Amazonis Planitia, due west of the volcano Olympus Mons, on Mars. It was identified by planetary geologist Peter Mouginis-Mark in September 2004. Scientists estimate that its age is on the order of hundreds of thousands of years, which is relatively young for a Martian crater. A later study confirms this order of magnitude estimate. A preliminary paper describing the geology and geometry of Tooting was published in 2007 by the journal Meteoritics and Planetary Science, vol. 42, pages 1615–1625. Further papers have been published, including a 2010 analysis of flows on the walls of Tooting crater by A. R. Morris et al., and a 2012 review paper by P.J. Mouginis-Mark and J.M. Boyce in Chemie der Erde Geochemistry, vol. 72, p. 1–23. A geologic map has also been submitted in 2012 to the U.S. Geological Survey for consideration and future publication.
The Great Daylight Fireball was an Earth-grazing fireball that passed within 57 kilometres of Earth's surface at 20:29 UTC on August 10, 1972. It entered Earth's atmosphere at a speed of 15 kilometres per second (9.3 mi/s) in daylight over Utah, United States and passed northwards leaving the atmosphere over Alberta, Canada. It was seen by many people and recorded on film and by space-borne sensors. An eyewitness to the event, located in Missoula, Montana, saw the object pass directly overhead and heard a double sonic boom. The smoke trail lingered in the atmosphere for several minutes.
A meteor air burst is a type of air burst in which a meteoroid explodes after entering a planetary body's atmosphere. This fate leads them to be called fireballs or bolides, with the brightest air bursts known as superbolides. Such meteoroids were originally asteroids and comets of a few to several tens of meters in diameter. This separates them from the much smaller and far more common "shooting stars", that usually burn up quickly upon atmospheric entry.
Neuschwanstein was an enstatite chondrite meteorite that fell to Earth on 6 April 2002 at 22:20:18 GMT near Neuschwanstein Castle, Bavaria, at the Germany–Austria border.
An Earth-grazing fireball is a fireball, a very bright meteor that enters Earth’s atmosphere and leaves again. Some fragments may impact Earth as meteorites, if the meteor starts to break up or explodes in mid-air. These phenomena are then called Earth-grazing meteor processions and bolides. Famous examples of Earth-grazers are the 1972 Great Daylight Fireball and the Meteor Procession of July 20, 1860.
The Chelyabinsk meteor was a superbolide that entered Earth's atmosphere over the southern Ural region in Russia on 15 February 2013 at about 09:20 YEKT. It was caused by an approximately 18 m (59 ft) diameter, 9,100-tonne (10,000-short-ton) near-Earth asteroid that entered the atmosphere at a shallow 18.3 ± 0.4 degree angle with a speed relative to Earth of 19.16 ± 0.15 kilometres per second. The light from the meteor was briefly brighter than the Sun, visible as far as 100 km (60 mi) away. It was observed in a wide area of the region and in neighbouring republics. Some eyewitnesses also reported feeling intense heat from the fireball.
The Chelyabinsk meteorite is the fragmented remains of the large Chelyabinsk meteor of 15 February 2013 which reached the ground after the meteor's passage through the atmosphere. The descent of the meteor, visible as a brilliant superbolide in the morning sky, caused a series of shock waves that shattered windows, damaged approximately 7,200 buildings and left 1,491 people injured. The resulting fragments were scattered over a wide area.
On 13 October 1990, meteoroid EN131090, with an estimated mass of 44 kg, entered the Earth's atmosphere above Czechoslovakia and Poland and, after a few seconds, returned to space. Observations of such events are quite rare; this was the second recorded using scientific astronomical instruments and the first recorded from two distant positions, which enabled the calculation of several of its orbital characteristics. The encounter with Earth significantly changed its orbit and, to a smaller extent, some of its physical properties.
Bunburra Rockhole is an anomalous basaltic achondritic meteorite. Originally classified as a eucrite, it was thought to belong to a group of meteorites that originated from the asteroid 4 Vesta, but has since been reclassified based on oxygen and chromium isotopic compositions. It was observed to fall on July 21, 2007, 04:43:56 local time, by the Desert Fireball Network (DFN). Two fragments weighing 150g and 174g were recovered by the DFN at 31°21.0′S, 129°11.4′E in the Nullarbor Desert region, South Australia in November of the same year. This is the first meteorite to be recovered using the Desert Fireball Network observatory.
Mason Gully is an ordinary chondrite of subclass H5, and is the second meteorite to be recovered using the Desert Fireball Network (DFN) camera observatory. One stone weighing 24.5g was observed to fall by the Desert Fireball Network observatory in Western Australia on 13 April 2010 at 10h36m10s UTC. It was recovered by the DFN on 3 November 2010 by Dr. R. Merle and the Fireball network recovery team, and was found 150m from its predicted fall location based upon the observed trajectory and calculated mass.
Murrilli (Moo-da-lee) is an ordinary chondrite of subclass type H5. It is the third meteorite to be recovered using the Australia Desert Fireball Network (DFN) camera observatory. It was observed to fall on 27 November 2015 at 9:15pm local time in South Australia, and recovered by the DFN team on 31 December 2015 from Lake Eyre. As this region is a salt lake, the 1.68 kg rock punched a hole through the ground and was found 0.43 m below the surface. It was recovered 218m from the predicted fall line location.
Dingle Dell is a 1.15 kg ordinary chondrite of subclass L/LL5, and the fourth meteorite to be recovered by the Desert Fireball Network camera observatory. It fell in the Morawa region of Western Australia on 31 October 2016 8:05 pm local time, and was recovered less than a week later, on the morning of 7 November, in a paddock at Dingle Dell farm. Given the rapid turnaround for meteorite recovery and a lack of rainfall between fall date and find date, the rock is in pristine condition and shows no evidence of terrestrial weathering (W0). This particular meteorite fall demonstrates the proficiency of the DFN as a sample recovery tool for meteoritics.
2018 LA, also known as ZLAF9B2, was a small Apollo near-Earth asteroid 2.6–3.8 m (9–12 ft) in mean diameter that impacted the atmosphere with small fragments reaching the Earth at roughly 16:44 UTC on 2 June 2018 near the border of Botswana and South Africa. It had been discovered only 8 hours earlier by the Mount Lemmon Survey, Arizona and based on 1+1⁄2 hours of observations, was calculated to have a roughly 85% chance of impact likely somewhere between Australia and Madagascar.
The Fireball Recovery and InterPlanetary Observation Network is a fully automated observation network of cameras and radios based in France that monitors the sky for fireball meteors. Using FRIPON, scientists can detect incoming meteors, determine their trajectory and estimate their strewn fields so that recovery operations of any surviving debris can be made. Currently, the FRIPON network operates across Western Europe and small sections of Canada, consisting of 150 cameras and 25 radio receivers that in total cover an area of nearly 1,500,000 square kilometres (580,000 sq mi). Formed in 2016, it is a collaboration between the Paris Observatory, the French National Centre for Scientific Research, the National Museum of Natural History and Paris-Sud University and has detected nearly 4000 meteoroids since 2020. FRIPON is the first fully automated high-density meteor observation system and is capable of quickly estimating a meteorite's strewn field to a 1 by 10km area.