53 research outputs found
Murrili meteorite's fall and recovery from Kati Thanda
On the 27th of November 2015, at 10:43:45.526 UTC, a fireball was observed
across South Australia by ten Desert Fireball Network observatories lasting 6.1
s. A kg meteoroid entered the atmosphere with a speed of
13.68\pm0.09\,\mbox{km s}^{-1} and was observed ablating from a height of 85
km down to 18 km, having slowed to 3.28\pm0.21 \,\mbox{km s}^{-1}. Despite
the relatively steep 68.5 trajectory, strong atmospheric winds
significantly influenced the darkfight phase and the predicted fall line, but
the analysis put the fall site in the centre of Kati Thanda - Lake Eyre South.
Kati Thanda has metres-deep mud under its salt-encrusted surface.
Reconnaissance of the area where the meteorite landed from a low flying
aircraft revealed a 60 cm circular feature in the muddy lake, less than 50 m
from the predicted fall line. After a short search, which again employed light
aircraft, the meteorite was recovered on the 31st December 2015 from a depth of
42 cm. Murrili is the first recovered observed fall by the digital Desert
Fireball Network (DFN). In addition to its scientific value, connecting
composition to solar system context via orbital data, the recover demonstrates
and validates the capabilities of the DFN, with its next generation remote
observatories and automated data reduction pipeline
On the missing single collision peak in low energy heavy ion scattering
We present experimental and simulation data on the oblique angle scattering of heavy Sn ions at 14 keV energy from a Mo surface. The simulations are performed with the binary collision approximation codes TRIM, TRIDYN, TRI3DYN, SDTrimSP, and IMSIL. Additional simulations were performed in the molecular dynamics framework with LAMMPS. Our key finding is the absence of an expected peak in the experimental energy spectrum of backscattered Sn ions associated with the pure single collision regime. In sharp contrast to this, however, all simulation codes we applied do show a prominent single collision signature both in the energy spectrum and in the angular scatter pattern. We discuss the possible origin of this important discrepancy and show in the process, that widely used binary collision approximation codes may contain hidden parameters important to know and to understand.</p
Where Did They Come From, Where Did They Go: Grazing Fireballs
For centuries extremely long grazing fireball displays have fascinated observers and inspired people to ponder about their origins. The Desert Fireball Network is the largest single fireball network in the world, covering about one third of Australian skies. This expansive size has enabled us to capture a majority of the atmospheric trajectory of a spectacular grazing event that lasted over 90 s, penetrated as deep as âŒ58.5 km, and traveled over 1300 km through the atmosphere before exiting back into interplanetary space. Based on our triangulation and dynamic analyses of the event, we have estimated the initial mass to be at least 60 kg, which would correspond to a 30 cm object given a chondritic density (3500 kg m-3). However, this initial mass estimate is likely a lower bound, considering the minimal deceleration observed in the luminous phase. The most intriguing quality of this close encounter is that the meteoroid originated from an Apollo-type orbit and was inserted into a Jupiter-family comet (JFC) orbit due to the net energy gained during the close encounter with Earth. Based on numerical simulations, the meteoroid will likely spend âŒ200 kyr on a JFC orbit and have numerous encounters with Jupiter, the first of which will occur in 2025 January-March. Eventually the meteoroid will likely be ejected from the solar system or be flung into a trans-Neptunian orbit
Recreating the OSIRIS-REx Slingshot Manoeuvre from a Network of Ground-Based Sensors
Optical tracking systems typically trade-off between astrometric precision
and field-of-view. In this work, we showcase a networked approach to optical
tracking using very wide field-of-view imagers that have relatively low
astrometric precision on the scheduled OSIRIS-REx slingshot manoeuvre around
Earth on September 22nd, 2017. As part of a trajectory designed to get
OSIRIS-REx to NEO 101955 Bennu, this flyby event was viewed from 13 remote
sensors spread across Australia and New Zealand to promote triangulatable
observations. Each observatory in this portable network was constructed to be
as lightweight and portable as possible, with hardware based off the successful
design of the Desert Fireball Network.
Over a 4 hour collection window, we gathered 15,439 images of the night sky
in the predicted direction of the OSIRIS-REx spacecraft. Using a specially
developed streak detection and orbit determination data pipeline, we detected
2,090 line-of-sight observations. Our fitted orbit was determined to be within
about 10~km of orbital telemetry along the observed 109,262~km length of
OSIRIS-REx trajectory, and thus demonstrating the impressive capability of a
networked approach to SSA
The Winchcombe meteorite, a unique and pristine witness from the outer solar system.
Direct links between carbonaceous chondrites and their parent bodies in the solar system are rare. The Winchcombe meteorite is the most accurately recorded carbonaceous chondrite fall. Its pre-atmospheric orbit and cosmic-ray exposure age confirm that it arrived on Earth shortly after ejection from a primitive asteroid. Recovered only hours after falling, the composition of the Winchcombe meteorite is largely unmodified by the terrestrial environment. It contains abundant hydrated silicates formed during fluid-rock reactions, and carbon- and nitrogen-bearing organic matter including soluble protein amino acids. The near-pristine hydrogen isotopic composition of the Winchcombe meteorite is comparable to the terrestrial hydrosphere, providing further evidence that volatile-rich carbonaceous asteroids played an important role in the origin of Earth's water
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