3D Software to Evaluate very low angle Impacts, Skip Impacts,
John A. Burgener, Telegistics Inc., john@burgener.ca
|
3D Skip Impact Program: Real time or faster viewing of skip impacts, the debris formed from such events, and the secondary craters formed from the debris. |
Swift Tuttle impact, sped up 200X. 
SkipImpact program showing debris shortly after impact. 
SkipImpact program showing debris trails after impact. The SkipImpact program is intended to show the effects of skip type impacts with a focus on the debris not the craters. It has several sets of simulations: 
1. A series of simulations showing skip impacts from different approaches of comets matching approach from above (such as Swift Tuttle), from behind, and from head-on, viewed from away from Earth allowing the impact itself to be viewed. 
2. A series of simulations showing the resultant orbits of the debris, with a view from far from the sun, allowing the full Swift Tuttle and other comet orbits to be portrayed. 
3. A series of simulations showing the secondary impacts and distribution of debris as it falls on Earth. 
4. An interactive simulation showing how comets impacting Earth can form circular to elliptical craters. It calculates thousands of impacts and presents the resultant craters for all angles and various sizes of comets. It allows you to enter a comet size, starting point and starting speed to see how that effects the final crater shape. The SkipImpact program is fully 3D and allows one to enter start positions and velocities for a range of comet sizes and see how they impact Earth in the interactive portion of the program. More importantly, it is able to demonstrate in detail how the debris from a skip impact would spread across the planet and the speed, impact angles and size distributions of the secondary craters formed by the debris as it lands on Earth. The program starts with comets made of up to 90,000 independent particles, each starting with the same speed and direction, then applying gravity and time to them. There is no program control of how or where the particles go other than the starting point. While the program can start with different speeds and directions, the resultant travels and impacts are all just a simple calculation of speed, gravity and time. The splashes are also up to 90,000 points with various approaches of applying starting speeds and directions according to the various parts of the splash. While the start speeds and directions may be imperfect assumptions, the resultant paths and impacts are simple math. The program considers comets to be similar to pumice, with high porosity, low density (0.5 – 1), and low structural integrity. As such, any portion hitting Earth will interact with Earth, but portions not hitting Earth will continue on with minimal effect. A comet skip impact is not like a ball bouncing but more like a handful of flour being tossed at the edge of a wall with part stopping and part moving on without noticing the part that stopped. Many of the low angle crater shapes calculated by the program are unexpected. Long, non-circular or elliptical patterns occur for skip impacts and impacts of less than 5 degrees. The images of the 4th option (Press Ctrl A at the start menu) show the planet covered with craters. They are created by setting up an array of thousands of comets approaching Earth in a grid array, spaced several comet diameters apart. They are all started at a selectable initial speed at 200,000 km from Earth and allowed to have gravity pull them to Earth or past Earth. The result is a planet covered with craters with impact angles ranging from 0 to 90 degrees, and shapes from circles to long sausage shapes. 
The shapes are calculated on the assumption that as part of the comet interacts with Earth, that part will leave an impression related to the size of the comet part in contact (usually 3X the comet size, but selectable to other factors). As such, as the bottom hits, a small circle will form. As the middle hits, a larger circle will form, as the top hits, another small circle forms. If the top of the comet does not hit, then the last part of the impression will be as wide as the last part hitting. With the planet curved, the part hitting varies as the comet moves forward. For low angles, the end result is ellipses or long partial ellipsoidal features with sometimes a wide end or beginning to narrow end. The program's calculations show realistic shapes for the craters in the 10 to 90 degree impact range, and it is probable that the unexpected long sausage shapes are also valid calculated crater shapes. The 3D array of impacts is educational and useful to validate the shapes of craters presented as secondary impacts. The secondary craters associated with a skip impact that would occur in the Carolina Bays areas are the same as the observed shapes of the Carolina Bays. 
SkipImpact program showing distribution of debris a few hours after impact. 
SkipImpact program showing distribution of debris 48 hours after impact from different views, with debris highlighted. The SkipImpact program is also useful to see how a skip impact would send debris around the planet. The program allows the debris to travel out to space and return for the portions that are below escape velocity. The final distribution shows that such an impact would rain hot debris over most of North America, South America, and Eurasia. Africa has little, and Australia has very few pieces of debris land, but very small particles from the shock waves would travel in all directions and could land anywhere and are not considered in this simulation. |
3D Skip Impact Program used to evaluate Comet Swift-Tuttle and its associated Fireball orbits which indicate a recent event with Swift-Tuttle impacting Earth. |
340 fireball orbits associated with Comet Swift Tuttle. Image by William Cooke, NASA Meteoroid Environment Office / All Sky Fireball Network, August 15, 2015. Fireballs are larger objects often related to debris from comets and most commonly seen as part of a meteor shower. The image of the 340 fireball orbits associated with comet Swift Tuttle shows a wide range of orbits, equally distributed between short and long orbits, only having the common feature of intersecting Earth's Orbit. If the fireballs are debris due to outgassing / disintegration of the comet as it passes close to the sun, then the orbits should concentrate along the orbital path of the comet. William Cooke considers the observed distribution as expected from a comet's outgassing and the debris being perturbed by the larger planets, disrupting the concentration along the comet's orbit. The SkipImpacts computer program allows one to calculate the possibilities of debris forming from outgassing or from a skip impact with Earth. The program includes calculating the effect of the debris orbits being perturbed by gravity of the planets and shows that outgassing / disintegration on orbit alone leaves a large concentration of orbits close to the comet's orbit. The planets' effects is mainly to move the debris orbits away from Earth Crossing orbits, leaving areas with few orbits of the debris orbit paths. The simulation of skip impact produces a wide range of orbits, matching what is observed. 
Debris points from outgassing over 27,000 years. 
Orbital paths of debris from outgassing over 27,000 years. Note the few orbits of debris scattered by the planets, and the large concentration of orbits closer to the comet's path. 
Debris from skip impact after 13,000 years. Note the areas with minimal debris caused by the planets scattering the debris from their original orbits. 
Orbital Paths of debris from skip impact after 13,000 years. The colors relate to debris particles that have been recently effected by planets, with blue = Earth, red = Mars, yellow = Jupiter, cyan=Saturn, bright green = Uranus, light green = Neptune, purple = not effected by a planet. Note the large number of paths far from the comet's path that are due to scatter of original orbits by planetary gravity effects. Such orbits would not show as fireballs related to the comet, instead they would be listed as random erratics. The wide range of orbital paths match what is observed of the fireball orbits associated with comet Swift Tuttle. W. Napier (2019) calculates that a 100 km diameter comet will disintegrate / outgass to less than 1 km diameter over 750 - 1500 orbits. With Swift Tuttle's orbit of 133 years, it is expected that it can not have existed for more than 200,000 years. If it has impacted Earth, the impact event must have occurred more recently than that. |
3D Skip Impact Program Comparison of secondary debris impacts and the Carolina Bays. |
The SkipImpact program has three simulations of large comets hitting North America in skip events that would form Lake Michigan or Lake Huron or the Saginaw Crater.
Lake Michigan is nearly identical in size and shape to the Orcus Patera crater on Mars. It is proposed that a skip impact hitting the ice sheets of North America, forming Lake Michigan, is also the source of the Carolina Bays. 
The Carolina Bays are tens of thousands of elliptical depressions along the east side of North America. It is heavily debated on when and how they formed. Image from Michael Davias, https://cintos.org/ The Carolina Bays are noted to be arranged in a very limited number of orientations, most pointing towards the Lake Michigan / Lake Huron area. 
Image from Michael Davias, https://cintos.org/ 
Image of proposed Lake Michigan impact. Michael Davidas' proposal of a single body's impact causing the Saginaw crater and the Carolina Bays as secondary impacts can fit the majority of Carilina Bays, but a multiple impact event with 4 or 5 bodies impacting the great lakes area, forming Lake Michigan and a part of Lake Superior will fit the observed Carolina Bays better. The debate on their origins relates to the mainstream consideration that they are wind erosional features, not impact related craters. The overlapping ellipses in different orientations are difficult to explain with wind erosion, but are expected from the secondary craters of debris from an impact of several pieces at the same time. The SkipImpact program produces thousands of debris particles tossed away from the crater, and is able to calculate their paths, including atmospheric drag and Earth’s rotation. The secondary impacts are displayed with the particle size, speed and impact angles listed for each secondary crater. 
Close up of SkipImpact program showing distribution of debris24 hours after impact. 
Next level of zoom in on debris along east coast of North America. 
When zoomed in more, the impact angle and speed is listed. 
More zoomed in to show the angles more clearly. Note that most are between 15 - 25 degrees and 3-4 km/sec. 
Images of craters with labels turned off to see more clearly the relationship of crater impact angles. The Carolina Bays have many overlapping craters that are slightly different orientations. The program predicts that this is expected with a Lake Michigan impact of several pieces of comet. iSALE shows that shapes matching the Carolina Bays would be formed by low speed impacts of 2 to 4 km/s, at average angles of 12 - 25 degrees. The SkipImpact program shows that a high number of secondary impacts fitting those speeds and angles will occur along the eastern coast of North America. 
iSALE images of low speed, low density impacts at various angles. The 15-25 degree angle impacts closely match the observed Carolina Bay shapes. The SkipImpact program uses four categories of debris tossed from the impact event. With these, some debris is tossed out into space at above escape velocity and leaves Earth. Some is tossed forward in line with the impact, but at lower speeds and sends debris forward. Some is tossed sideways as a bow wave (similar to what is seen at the front of a high speed boat) and this is what leads to the secondary crates along the east coast. Some debris is tossed in all directions from the shock waves of the impact. Such particles of debris can be sent anywhere on Earth, but will typically be smaller particles than what is required to make the Carolina Bays. Michael Davias and Thomas Harris propose that the Australasian Tekites are related to such a skip impact, and that is possible for particles tossed by the shock wave. The intent of the program is not to demonstrate a perfect rendentation of the debris, but to demonstrate that secondary craters from such an impact is reasonable. Can a skip impact produce secondary impacts from the debris? The answer is definitely YES. Do the secondary craters match the Carolina Bays? Again, YES. How much debris lands in the Carolina Bays area and forms mini craters depends on the size of the comet, the nature of the debris being tossed and the nature of the land it falls on. But a large comet forming Lake Michigan or the Saginaw crater COULD send debris that fits the size, speeds and impact angles required to form the Carolina Bays. |
Discussions and Conclusions |
The possibility of a skip impact is demonstrated by iSALE calculations. The following iSALE simulation shows that a comet CAN hit Earth and continue on its orbit. iSALE is accepted as geologically correct in calculating impact craters. However, it does not display the debris in detail and it requires days to months to simulate a complex, detailed impact.
iSALE presentation of a 5 degree impact, with part of the comet continuing on and part is shattered and tossed back into space as debris, mixed with a lot of debris from Earth. The size of comets being considered is large. At present, Swift-Tuttle is estimated to be 40 km in diameter. If it is the remnant of a skip impact, then the original comet was larger - likely in the order of 60 - 100 km in diameter. Asteroids are known to be smaller with very few in the asteroid belt over 10 km in diameter, so they are not being considered for potential skip impact events. However, it is becoming accepted that most comets come from the Kuiper Belt, and the bodies there are estimated to be 1000 times more abundant than asteroids, 100 times larger, and by the calculations of the effects of the dwarf planets on the Kuiper Belt objects (Burgener, 2019), they are often pushed out of their orbits into Earth Crossing orbits. The SkipImpact program is not intended to show cratering but instead is focused on the debris and secondary craters, and it runs in real time or very much faster, showing the impact events in minutes instead of weeks. It is a tool designed to help evaluate and simulate the debris produced in such an impact and any secondary craters from it.
The final distribution of hot debris falling from space and landing on Earth shows that a skip impact from Swift Tuttle forming Lake Michigan would also cause massive fires in several parts of Earth but not other areas. Australia and Africa have very little debris land there. It is recognized that most large animals in North America, South America and Eurasia went extinct about the same time as the end of the ice age, or about 12,700 years ago, but the large animals of Africa were not effected. The larger pieces of debris falling from space at 6+ km/s would have triggered fires where they landed, causing massive fires across the continents that had the extinctions occur. The SkipImpact program can highlight the debris falling at speeds above 6 km/s to more easily see the areas that would have fires set by the falling debris. Conclusion: The SkipImpact 3D software indicates that a skip impact by Comet Swift Tuttle would fit as the source of the Carolina Bays as secondary impacts from the impact debris, and would explain the distribution of the fireball orbits associated with the Perseid Meteor Shower. The program predicts that very low angle craters will be of unusual shapes and often not recognized due to their elongated and shallow shapes. Acknowledgments: We gratefully acknowledge the developers of iSALE-2D, including Gareth Collins, Kai Wünnemann, Dirk Elbeshausen, Tom Davison, Boris Ivanov and Jay Melosh, and we gratefully acknowledge the developers of iSALE-3D, including Dirk Elbeshausen, Kai Wünnemann, Gareth Collins and Tom Davison. References: [1]. Burgener (2022) SkipImpact.exe computer program simulating comet impacts in 3D with up to 90,000 points of debris being calculated in orbit over thousands of years. Available to download from www.craters.ca [2]: Cooke, W. (2014-2021), NASA’s All Sky Fireball Network daily charts of fireball orbits posted on www.spaceweather.com. Included fireball chart from Aug 2015: https://www.spaceweather.com/FIREBALL_PARSER/fireball_data.png?PHPSESSID=ik2r3o2g28eob2n25cpmlc49o4 [3]. Napier, W. P. (2019) "The hazard from fragmenting comets", MNRAS 488, 1822-1827 (2019). doi: 10.1093/mnras/stzl 769 [4] Davias, M., Harris, T. (2019) “An Incomprehensible Cosmic Impact at the mid Pleistocene Transition, Searching for the Missing Crater using Australasian Tektite Suborbital Analysis and Carolina Bay’s Major Axes Triangulation”; GSA Annual Meeting in Phoenix, Arizona, USA. DOI: 10.1130/abs/2019AM-332326 [5] Burgener, J. “The Influence of Dwarf Planets on the Stability of Objects in the Kuiper Belt”, 50th Lunar and Planetary Science Conference 2019, Presentation 3163. |
