The Observation of Lunar Impacts

The frequency and the characteristics of lunar impacting meteorites are reconsidered under the general assumption of belonging to the sporadic meteoroids. We develop the model for evaluating the luminous energy detected in the visual band during the impact. The values obtained are consistent with the luminosity of an Earth's meteor as seen at the Moon's distance, although we recover significantly smaller magnitudes for the lunar impacts with respect to other authors.

The frequency and the characteristics of lunar impacting meteorites are reconsidered under the general assumption of belonging to the sporadic meteoroids. We develop the model for evaluating the luminous energy detected in the visual band during the impact. The values obtained are consistent with the luminosity of an Earth's meteor as seen at the Moon's distance, although we recover significantly smaller magnitudes for the lunar impacts with respect to other authors. 1. The detection of lunar impacts Although the lunar transient phenomena (LTP) have been observed since several tens of years, it is only recently that they reached the dignity of a scientific problem. Thanks to the effort of some groups of scientists orchestrated by D. Dunham, it was possible to detect unambigously five flashes onto the night side of the Moon [1] during the Leonids meteor shower of 1999. The opportunity to detect other impacts out of known active showers has been taken into account in our first...

Earth, Moon, and Planets, 2000

Confirmed observations of meteoroids from the Leonid stream impacting the Moon in 1999 and 2001 have opened up new opportunities in observational and theoretical astronomy.

Icarus, 2006

We present the first redundant detection of sporadic impact flashes on the Moon from a systematic survey performed between 2001 and 2004. Our wide-field lunar monitoring allows us to estimate the impact rate of large meteoroids on the Moon as a function of the luminous energy received on Earth. It also shows that some historical well-documented mysterious lunar events fit in a clear impact context. Using these data and traditional values of the luminous efficiency for this kind of event we obtain that the impact rate on Earth of large meteoroids (0.1-10 m) would be at least one order of magnitude larger than currently thought. This discrepancy indicates that the luminous efficiency of the hypervelocity impacts is higher than 10 −2 , much larger than the common belief, or the latest impact fluxes are somewhat too low, or, most likely, a combination of both. Our nominal analysis implies that on Earth, collisions of bodies with masses larger than 1 kg can be as frequent as 80,000 per year and blasts larger than 15-kton could be as frequent as one per year, but this is highly dependent on the exact choice of the luminous efficiency value. As a direct application of our results, we expect that the impact flash of the SMART-1 spacecraft should be detectable from Earth with medium-sized telescopes.

Planetary and Space Science, 2012

Monitoring the Moon for impacts is a highly rewarding approach for studies of small asteroids and large meteoroids encountering the Earth-Moon System. The various effects of meteoroids impacting the Moon are described and results from different detection and study techniques are compared. While the traditional statistics of impact craters allow us to determine the cumulative meteoroid flux on the lunar surface, the recent successful identification of fresh craters in orbital imagery has the potential to directly measure the cratering rate of today. Time-resolved recordings, e.g., seismic data of impacts and impact flash detections clearly demonstrate variations of the impact flux during the lunar day. From the temporal/spatial distribution of impact events, constraints can be obtained on the meteoroid approach trajectories and velocities. The current monitoring allows us to identify temporal clustering of impacts and to study the different meteoroid showers encountering the Earth-Moon system. Though observational biases and deficiencies in our knowledge of the scaling laws are severe, there appears to be an order-ofmagnitude agreement in the observed flux within the error limits. Selenographic asymmetries in the impact flux (e.g., for equatorial vs. polar areas) have been predicted. An excess of impacts on the lunar leading hemisphere can be demonstrated in current data. We expect that future missions will allow simultaneous detections of seismic events and impact flashes. The known locations and times of the flashes will allow us to constrain the seismic solutions. While the numbers of flash detections are still limited, coordinated worldwide observations hold great potential for exploiting this observation technique. The potential for identification of fresh craters in high-resolution orbital image data has just barely been tapped, but should improve significantly with the LRO extended mission. 2 The Impactor Population The impactor population in the Earth Moon system is traditionally being monitored by telescopic observations of Near-Earth Objects (NEOs) (> 10 m) as well as by observations of the smaller meteoroids (< 10m) entering the Earth's atmosphere.

2016

In this experiment the shadow length of a crater wall and the Sun's zenith angle at the time of observation were used to calculate the depth of craters on the moon. We then calculated the impact energy of an asteroid to cause such craters. Finally we used these details to calculate an approximate range of the mass of asteroids hitting the moon. We also calculated an estimate for the total number of asteroids to hit the moon.

Earth, Moon, and Planets, 2000

The occurrence and visibility of meteoroid impacts on the moon as seen from the earth were little more than speculation prior to November 1999. The best evidence of present-day impact activity came from the seismic experiments left on the Moon during the Apollo era. Past systematic attempts at earth-based observations to document lunar impacts revealed nothing conclusive. However, during the Leonid storms of 1999 and 2001, lunar impact events were for the first time confirmed by multiple independent observers. A total of 15 meteoritic impact flash events have been verified during these storms, with an additional 12 unconfirmed but likely events awaiting confirmation. Estimates of the mass of these meteoroids range from less than one gram for the faintest flashes to more than 10 kg for the brightest observed flash. The fraction of visible light to total energy produced by these events, a quantity known as luminous efficiency, averages about 0.001 for the established events. The confirmation of lunar meteoritic events on the Moon opens a new avenue in lunar and planetary research, one which could help bridge the gap between atmospheric sampling of the smallest components of meteoroid streams and interplanetary debris to the larger scale objects accessible to ground-based telescopes.

Icarus, 2014

The flashes from meteoroid impacts on the Moon are useful in determining the flux of impactors with masses as low as a few tens of grams. A routine monitoring program at NASA's Marshall Space Flight Center has recorded over 300 impacts since 2006. A selection of 126 flashes recorded during periods of photometric skies was analyzed, creating the largest and most homogeneous dataset of lunar impact flashes to date. Standard CCD photometric techniques were applied to the video and the luminous energy, kinetic energy, and mass are estimated for each impactor. Shower associations were determined for most of the impactors and a range of luminous efficiencies was considered. The flux to a limiting energy of 2.5×10 -6 kT TNT or 1.05×10 7 J is 1.03×10 -7 km -2 hr -1 and the flux to a limiting mass of 30 g is 6.14×10 -10 m -2 yr -1 at the Moon. Comparisons made with measurements and models of the meteoroid population indicate that the flux of objects in this size range is slightly lower (but within the error bars) than flux at this size from the power law distribution determined for the near Earth object and fireball population by . Size estimates for the crater detected by Lunar Reconnaissance Orbiter from a large impact observed on March 17, 2013 are also briefly discussed.

2021

We have reviewed and analyzed the lunar luminous events observations by William Herschel during the peak of the Lyrid meteor shower of 1787 and Leon Stuart near the peak of the Leonid meteor shower of 1953, seeking the impact craters that these events presumably formed. Evidence is presented that identifies two cold spot fresh craters as the expected candidates.

2014