Brief summary of
recent results of Leonid MAC research.
SPECIAL ISSUE ASTROBIOLOGY
The journal Astrobiology has changed its traditional front cover to feature one of the spectacular fireballs photographed during the 2001 Leonid shower. This one is by Kris Asla from Aloha, Oregon. The issue features five papers that present results from the 2001 and 2002 Leonid MAC missions:
studies of the plasma temperature and temperature decay in the wake of meteors, and studies of CN, OH, and H emission that probe the exogenous delivery of organics and water.
March 14 - studies of meteor air plasma temperature
March 14 - the temperature decay in the wake of a meteor
March 14 - how carbon does not turn into CN
March 14 - how OH is not detected, but N2+ is a new discovery
March 14 - how Hydrogen atom emission serves as a marker for organics and water
JUNE BOOTID OUTBURST OBSERVED
An outburst of June Bootid meteors was observed from about June 22 19h UT
until June 24 01h UT (ZHR > 1/hr), peaking at a rate of ZHR ~ 30/hr at 11ÿý2 h
UT, 2004 June 23.
June 25 - June Bootid outburst observed
QUADRANTID PARENT OBSERVED AT ESO
The minor planet 2003 EH_1 was recovered with the New Technology Telescope at the European Southern Observatory on Christmas Eve. The object had not been seen since May. The new observations refine the orbit by a factor of about 100.
Dec 28 - Quadrantid parent observed at ESO
Dec 28 - Good Quadrantid show on 2004 Jan 04
QUADRANTID PARENT BODY DISCOVERED
The Quadrantids are the most intense annual shower, but also the only major shower without a known parent body. Now, the parent is identified as 2003 EH_1, a minor planet first seen by the Lowell Observatory Near-Earth Search on March 06, 2003.
Dec 08 - Quadrantid parent body identified
Several very old dust trails had been predicted to be in Earth's path during the 2003 Leonid return, but clouds hampered most observing efforts.
Read more: Nov 20 - Leonids hampered by clouds.
New high-frame rate images confirm the presence of a shock in the images
of bright Leonids.
Nov 23 - "Shock" confirmed
NEW MOLECULAR BAND DETECTED
Nice new spectroscopic data on meteors and their afterglow contain emission from
a new molecular band.
Nov 22 - New molecular band detected
A small camera was succesfully pointed rapidly at meteors from the DC-8 aircraft,
capturing the image of a bright -8 magnitude fireball.
Nov 21 - Leonids tracked
ASTEROIDS NAMED AFTER LEONID MAC PARTICIPANTS
Two asteroids were named after Leonid MAC organizers by the International Astronomical Union.
Nov 20 - Asteroids named after Leonid MAC participants
LEONID STORMS RICH IN FAINT METEORS
The 2002 Leonid storms returned much as predicted, but were surprisingly rich
in faint meteors. Best viewing was from aircraft.
Nov 19 - Leonid storms rich in faint meteors
COLLECTING METEORIC DEBRIS FROM SNOW COVER
Leonid meteoric debris can possibly be collected from snow fall in Antarctica and
Greenland. The micro meteorites are recovered by melting the snow
layer by layer, thus collecting meteoric debris from specific years.
Oct 22 - Meteoric debris from snow
COSPAR/WORLD SPACE CONGRESS HIGHLIGHTS
A special session on "Meteor Induced Chemistry, Ablation Products, and Dust in the
Middle and Upper Atmosphere" was organized as a joint COSPAR/IAC event at the
World Space Congress in Houston, TX, on October 16, 2002.
Oct 21 - COSPAR/WSC highlights
FIRST UV SPECTRUM: LEONID FROM SPACE
For the first time, a spectrum of a meteor was recorded in the ultraviolet, showing
strong emission lines of ionized and neutral magnesium. It is found that
the ionized line is a unique probe of the ionization conditions in the warm
Aug 31 - First UV spectrum: Leonid from Space
This year's Leonid MAC Workshop was held in Tokyo, Japan. Highlights of the scientific program are listed below.
GOOD PROSPECTS FOR NOVEMBER 2002
The interpretation of the meteor showers in terms
of the dust trails of comet 55P/Tempel-Tuttle has come of age.
Guest speaker Dr. Yoshihide Kozai
of Gunma Astronomical Observatory of Japan post-predicted a possible dust trail encounter in
1990 from recent dust trail modeling. Regarding the 2001 Leonid storm over Asia,
Toshifumi Yanagisawa of the National Aerospace Laboratory of Japan reported on
observations of meteor trails near the radiant that make it possible to separate the
1866 dust trail from older 1699 ejecta of comet 55P/Tempel-Tuttle.
Nov 24 - Results of near-real time flux measurements
Dec 01 - Moon impacts
SPECTACULAR BURST OF METEORS
During the 2001 Leonid storm, as many as 1400 highschool children participated in an
internet-based effort to gather flux measurements that map the spatial distribution
of dust accross Japan in high detail. Organiser Dr. Bunji Suzuki reported possible filamentary
structure in the shower over large spatial scales. Dr. Jun-ichi Watanabe of the National Optical
Observatory of Japan reported several detections of meteoroids that had
fallen appart recently in the interplanetary medium, creating spectacular local bursts of
15-40 meteors in just 2 seconds. Similar fragmentation processes may be responsible
for pairing in meteors reported by Juraj Toth of the Copernicus University of Bratislava
in Slovenia from an analysis of observations from the 1999 Leonid MAC mission.
THE COMET GAS PRODUCTION RATE
The meteor shower observations provide very accurate measurements of the dust ejected
by the comet in each return. At the workshop it was reported that
emissions from C2, NH2, and 630 nm OI line emission were observed in the comet
atmosphere during the 1998 return by Toshihiko Hamane of Gunma Astronomical
Observatory and colleages. A gas production rate of 320,000 g per second was derived
for the time of the observations.
NEW METEOR EMISSION MECHANISM DISCOVERED
Dr. Jiri Borovicka of Ondrejov Observatory
reported the discovery of recombination line emission in spectra of bright Leonid
fireballs. This phase of the meteor's light decay followed directly on the afterglow
that was discovered in the 1999 Leonid MAC mission. Spectacular spectra of this
recombination emission were obtained as well by Japanese amateur astronomer
Oct 26 - Persistent train emissions
OH EMISSION IN METEORS DISCOVERED
Dr. Shinsuke Abe and coworkers of ISAS reported
the detection of emission at 310 nm, of what appears to be the A-X OH emission. This
emission points at the presence of water in the meteoroid or in the ambient atmosphere.
STRONG LOWER LIMIT ON CN PRODUCTION
Dr. Peter Jenniskens and Dr.
Rick Rairden of Lockheed Palo ALto reported very strong
upper limits to the production of the CN radical, expected from the decomposition
of organic matter in the meteor, bringing down by a factor of 10 the amount of CN that
is produced. Those limits strongly raise the likelyhood that meteors may have
contributed organic matter to the early Earth at the time of the origin of life.
Oct 22 - Whow! Meteor optical spectra
RADAR REFLECTION SIGNATURE CHANGE
Dr. Nakamura of the MU Radar facility
in Kyoto, Japan, reported the first simultaneous observations of optical meteors and
radar reflections. It was found that many echoes had a rapid decline in intensity halfway
through the meteor's path. This is interpreted as a result of changing reflection conditions.
HIGH FRAMERATE IMAGES SHOW UNEXPLAINED SHOCK
Dr. Hans Stenbeak Nielsen of the University of
Alaska at Fairbanks reported on further
analysis of the high framerate images of Leonid meteors. The position of what looks
like a shock has now been identified, but we are far from understanding the spectacular
features in the meteor images.
Dec 11 - Shocking Leonid
LEONID SHOWER UNEXPECTEDLY GOOD FOR USA OBSERVERS
Analysis of 2000 Leonid shower observations by Peter Jenniskens of
the SETI Institute at NASA Ames Research Center confirm earlier
suspicions that the pattern of dust trails is slightly shifted towards
the Sun compared to calculations by Esko Lyytinen and David Asher.
This is good news for observers in Northern America, because
peak rates are now predicted to be the same as during the 1999 Leonid storm
at ZHR = 4,200 per hour.
Observers in the western Pacific and Australia will not be disappointed
either. The predicted peak rates are nearly as strong (ZHR = 3,700 per
hour) and the trails are slightly wider, making these 1699- and 1866-dust
trail encounters combined the more rich display by about 60 percent.
METEORS AND THE ORIGIN OF LIFE ON EARTH
In a paper submitted to the proceedings of the 2001 Meteoroids conference
in Kiruna, Sweden, Peter Jenniskens gives a review of recent
studies on the fate of organic matter in meteors. Full paper.
LEONID STORM RESEARCH
Support the research: Order
directly from contributing Leonid MAC researchers your special issue
of the journal Earth Moon and Planets "Leonid Storm Research",
with over 40 articles on the 1998 and 1999 Leonid shower research
URSIDS: DUST FROM TIME OF COLUMBUS ABOUT TO HIT
EARTH ON DECEMBER 22, 2000
Dec. 18 - Dec 22 Ursid outburst
Dec. 23 - Ursid outburst confirmed
Dec. 24 - Ursid shows early release of sodium
Dec. 25 - Ursid shower circular IMO
TWIN SHOWERS DURING UPCOMING 2000 LEONID ENCOUNTER
New modeling predict that not one, but two sharply peaked Leonid showers will
be visible in the nights of November 16/17 and 17/18, when Earth passes
by the dust trails produced in the 1932 and 1866 returns of parent comet
55P/Tempel-Tuttle. Models suggest that the second night will be the better
one, but analysis of last year's flux measurements onboard the Leonid MAC
seem to indicate that the pattern is slightly shifted and the first night
may be the better one. Rates can go up to Perseid shower levels or higher,
with best viewing over the eastern USA at about 7:50 UT (2:50 EST).
Californian observers can catch a glimpse of it around midnight.
A tool is on the net that people can use to see how much activity is expected
from their observing location.
LIFE's PRECURSORS CAN SURVIVE PLUNGE IN ATMOSPHERE
Not all meteoric matter is atomized during the plunge in Earth's
atmosphere. Organic matter remained mysteriously undedected during last
year's Leonid MAC. In a recent paper, Jenniskens et al. postulated that
the organic matter may be lost in the form of large complex molecules that can
readily emit the heat deposited by the violent collisions with air
molecules before falling appart altogether. Such large molecules are not
easily detected, except by their heat emission. Indeed, Ray Russell et al. discovered the fingerprint of organic matter in
what may be meteoric debris in the path of a bright Leonid fireball.
Pointing the mid-IR telescope onboard FISTA to the persistent train of the fireball,
emission at 3.4 micron was detected that resembles the signature
of complex organic matter observed in cometary dust. However, at
present it can not be excluded that trace air compounds are responsible.
Nov. 13 - Organic fingerprint
Nov. 20 - A bacterial fingerprint?
METEOR SHOWER FROM SPACE
Spectacular images of a meteor shower from space were released with
the publication of a special issue of Earth, Moon and Planets. The images
are a composite of numeous Leonid fireballs as seen from the MSX satellite
near the limb of the Earth.
Nov. 14 - Meteor shower from space
METEOR TRAINS REVEIL SECRETS
Fast meteors that are bright enough leave persistent trains in the sky
that are an eary trace of the brilliance of the meteor. "Glowworms"
doubht by some, these trains have long kept their secret of why the
glow persists for such a long time. Now, during Leonid MAC the light
of such trains was unraveled (work by Borovicka and Jenniskens), reveiling
an orange continuum emission band. Comparisson with laboratory measurements
by John Plane (Univ. East Anglia) shows that iron oxide emission is
responsible for the broad band emission, while sodium emission is detected
too. Sodium and iron atoms catalyse the recombination of oxygen
atoms and ambient ozone molecules back into molecular oxygen, being
excited in the process. A similar chemistry is responsible for the airglow
that is seen on the limb of the Earth. The trains can thus probe
this important chemistry under unusual conditions.
Nov. 12 - Train airglow chemistry
Nov. 11 - Hard bits and persisting glows
DEBRIS DETECTED IN AFTERGLOW OF FIREBALL
For the first time, solid meteoric debris was detected in the afterglow of
a bright Leonid fireball by Borovicka et al. A continuum black body
emission betrayed this long sought after evidence that meteors do
not totally obliterate when entering the Earth's atmosphere.
The matter appeared to continue ablation at T ~ 1,400 K, and descended to
lower altitude after it was deposited, when it was detected as a glowing
emission in the path of the meteor. Numerous neutral atom emission were
observed also, from which a rapid cooling was measured from about 4,500 K
to 1,200 K in two seconds.
Until now, meteoric debris was known only from asteroid-type fireballs that
penetrated deep into the atmosphere. Now, for the first time, debris was observed
of cometary matter. The high speed of the meteor makes it surprising that
any matter at all could survive the plunge in Earth's atmosphere.
Nov. 10 - Meteoroid debris detected
Meteors not has hot as thought before.
The first temperature measurements from the blazing light of Leonid
meteors by Jenniskens et al.
show that most of the visible light of meteors comes from a
rather cool wake behind the meteoroid's head. At 4,300 K, that wake is
not as hot as thought before and has just the right temperature for the
chemical breakup of C-O, leading to potentially interesting organic
chemistry in Earth's early atmosphere.
Nov. 09 - New meteor picture
METEORS SPROUT TINY OFFSPRING
During last year's Leonid campaign it was discoved that Leonid
meteors sprout mysterious jets of light in all directions when they come
blazing into the Earth's atmosphere. Now, Mike Taylor et al. onboard
Leonid MAC was able to prove that these jets are caused by small meteoroid
fragments that are ejected with stupendous speeds, up to 2 km/s,
from a tumbling mass of fragments caused by the evaporation
of a "glue" that keeps the meteoroid together in space. Earlier
detections in the 1998 Leonid MAC were made in white light. By using
narrow band imaging, Taylor looked specifically for light from the meteoric
magnesium, and found those jets of light to be even more prominent, proving
that the jets are caused by small fragments of meteoric matter.
Nov. 08 - Spin city
ATMOSPHERE GETS A JOLT FROM LEONID STORM
Joe Kristl et al. report an increase in OH airglow emission during the peak
of the Leonid shower. No such change was observed for sodium emission and
O2 airglow emissions. It is not clear yet how the enhanced influx of meteoric
matter caused the change in airglow chemistry.
Despois et al. observed a decline of HCN molecules in the upper atmosphere
one day after the Leonid storm.
Nov. 07 - Meteors affect atmospheric chemistry
Nov. 15 - HCN disappears mysteriously
METEORS EMIT LOW FREQUENCY RADIO WAVES
A long standing controversie may finally have been settled. Numerous eye
witnesses of bright fireballs in the past reported hissing and sissing sounds
while watching the light of the meteor. Because it takes sound some time to
travel from the meteor to the observer, it was long thought that meteors
may emit low frequency radio waves that could induced audible sounds in
nearby objects or the observers glasses, tooth fillings, etc. Now, Israeli
observers Colin Price and Moshe Blum report the detection of ELF/VLF
signals of unusual spectral character, peaking at the time of the 1999 Leonid
meteor storm. It appears that even visible meteors produce detectable radio
emissions. The signals are of unusually short duration (10 msec) and it is
not clear yet how the signals are made.
Nov. 06 - Listen to this!
Nov. 04 - Fear of heights?
Nov. 03 - The pale (infra-red) dot
Nov. 02 - Twin showers
Nov. 01 - Leonids approaching Earth
Oct. 31 - Prospects for Moon Impact Studies
DURING 1999 METEOR STORM, COMET DUST CRUMBLED LESS FINE
Ian Murray et al. discovered from imaging onboard Leonid MAC that Leonids in
the 1999 encounter fell appart in relatively larger fragments than did
Leonids during the 1998 encounter. Both the 1998 and 1999 Leonid light curves
were flat-topped, implying that the meteoroids quickly fell appart in
fragments upon entry in the Earth's atmosphere, but the 1998 light curves
tended to peak early in the trajectory followed by a gradual fading,
while the 1999 light curves gradually ramped up to a late peak. The cause
of this unexpected behaviour is not understood. Both encounters were with
dust ejected in 1899. We now look forward to an encounter with the dust
trail of 1932 on November 16/17, 2000.
Oct. 30 - Comet dust crumbled less fine