Appendix A: the Maribo Meteorite

Appendix A: The Maribo Meteorite Although the Maribo meteorite may ultimately have come from Comet Encke, or the hypothetical comet from which Encke and the Taurid meteor complex is widely thought to have originated, the more recent history of this object appears to associate it with several other minor Solar System bodies. As mentioned in the main text, there appears to be a strong association (as determined by Drummond’s D′ criterion) with the Apollo asteroid 85182. But the associations do not cease there. In their paper published in The Observatory (1994 October), Duncan I. Steel and David Asher distinguished two groups of Apollo asteroids; the larger of the two pursuing orbits similar to those of the Taurid meteors and the smaller having orbital ele- ments similar to those of the asteroid (2212) Hephaistos. These apparent families were simply called the Taurid group and the Hephaistos group respectively. As noted in Chap. 1 of the present book, each group also includes a comet; Encke in association with the former and Helfenzrieder in association with the latter. Encke remains an active object, but Helfenzrieder was observed (as a relatively bright naked-eye object sporting a long tail) only during its 1766 apparition. This object was probably dormant at earlier returns and possibly broke apart in 1766, going out in an uncharacteristic blaze of glory. Any remnant that may continue to exist today is presumably small and very faint although some day it may be discovered anew by one of the search programs seeking near-Earth objects. Steel and Asher found that the two asteroid groups distinguished themselves most readily through the respective ranges of longitude of perihelion of their members’ orbits. This value is the sum of the argument of perihelion and longitude of the ascending node of the orbit and can be thought of as the orbit’s orientation. Taurid group orbits have longitude of perihelion values between 100° and 190° whereas Hephaistos group orbits fall between 222° © Springer International Publishing Switzerland 2016 257 D. Seargent, Weird Astronomical Theories of the Solar System and Beyond, Astronomers’ Universe, DOI 10.1007/978-3-319-25295-7 258 Appendix A: The Maribo Meteorite and 251°. These limits have no magical significance: they are simply the values between which the objects of each group that were known in 1994 fell. Steel and Asher opined that other objects fall- ing within the gap may eventually be found, effectively turning the two groups into concentrations at each end of a single extended family. This latter scenario would actually fit with what Steel and Asher see as the dynamical history of these groups. With respect to perihelion distance, eccentricity and inclination, the orbits of the members of both groups are at the same time similar to one another and yet different from the typical Apollo asteroid. As argued in the main text of the present book, there are reasons to think that a number of the objects included within the Taurid group might, however, by interlopers, but that does not alter the basic model. Some, at least, of the suspected interlopers have orbits which are less typical of the Taurid group than those of the “core” members. In any case, the atypical orbits of members of both groups are best explained, according to Steel and Asher, if the entire complex originated in the prehistoric disruption of a large periodic comet. The comet initially split into two major pieces, each of which progressively broke up over many perihelion pas- sages. The Taurid group represents the fragments of the principal nucleus and the Hephaistos group consists of the fragments of the main secondary comet. Presumably all of the asteroids were once active comets that have now become dormant through the build- up of an insulating layer on their surfaces. Maybe Encke was dormant for many years but became active again prior to its discovery through (we might suppose) the fracturing of its insulating layer. Helfenzrieder may have suffered a worse catastrophe, activating in an extreme way at a single return and then fading out completely. As mentioned in Chap. 1 , the Maribo meteorite appears to be a member of the Hephaistos group. Its longitude of perihelion is 217°, a little toward the Taurid side of the lower limit given in the Steel/Asher paper although, as we said, there is nothing absolute about this lower limit. Their lower value appears to have been set by the asteroid 85182 (222°) which we suggested is the immediate parent body of the meteorite. Further examination yielded an even bigger surprise however. This asteroid seems to be the parent object of the Delta Cancrid Appendix A: The Maribo Meteorite 259 meteor shower and the Maribo meteorite is a member of this shower. If this is confirmed, it represents the clearest association yet discovered between a meteor shower and a meteorite. Taking the orbit of the shower as being the average of three orbits published by Gary Kronk in his Meteor Showers: A Descriptive Catalog (1988), we find the following; Longitude of perihelion of Delta Cancrids = 222.3° Delta Cancrid/Maribo meteorite, D′ = 0.0717 Delta Cancrid/asteroid 85182, D′ = 0.0821 Maribo/asteroid 85182, D′ = 0.04 Looking at the three individual orbits noted by Kronk; S1973/asteroid 85182, D′ = 0.0803 S1976/asteroid 85182, D′ = 0.115 L1971B/asteroid 85182, D′ = 0.0595 S/1973/Maribo, D′ = 0.066 S1976/Maribo, D′ = 0.1086 L1971B/Maribo, D′ = 0.0379 The orbit for the southern Delta Cancrids noted by Kronk did not fare so well, yielding D′ values for 85182 and Maribo of 0.1651 and 0.1581 respectively. Considering the degree of scatter expected in this meteor stream however, that is probably not too surprising. It is interesting to note that Maribo fell on January 17, the date usually given for maximum of the Delta Cancrid shower. Moreover, the velocity of the Delta Cancrid meteors has been measured as 28 km/s in excellent agreement with that of Maribo. Orbits having Drummond D′ values of 0.105 or less are indicative of association. The case for the above suggested associations, therefore, appears to be rather strong. Appendix B: The Sutter’s Mill Meteorite: A Taurid Connection? In terms of its longitude of perihelion, high eccentricity, small inclination and a perihelion distance near the orbit of Mercury, the orbit of the Sutter’s Mill meteorite is indicative of a Taurid association. Yet, that is not obvious from its date of fall; April 22, 2012. A search of meteor showers published by Kronk neverthe- less uncovered something interesting. He lists a daytime shower (May Arietids) extending from early May until early June and gives three orbits as determined by radio observations made during the 1960s. All of these orbits show some similarity with that of Sutter’s Mill. The early date of the meteorite does not necessar- ily count against association with the stream, as it is not unusual for weak activity to extend beyond the limits normally given for meteor showers. Taking an average of the orbits given by Kronk and comparing this against that of Sutter’s Mill yields a D′ value of 0.097. Equally intriguing is the comparison between the average May Arietid orbit and the one computed by Kronk for the southern Taurids. This comparison yields D′ = 0.094. The May Arietids probably have a southern and a northern branch and the orbits given by Kronk seem more representative of the northern branch. From the apparent association with the southern Taurids, it appears that this northern branch of the May Arietids (though not as well established as the southern one) forms part of the same stream as the southern Taurids. When Earth encounters the stream members on their way toward perihelion—which happens during October and November—those mete- oroids which then enter our atmosphere are observed as southern Taurids. When Earth intercepts part of the same stream on the outward journey around May and June, some encounter our planet as northern May Arietids. In this connection, it is interesting to note that Sutter’s Mill arrived at perihelion just over six weeks © Springer International Publishing Switzerland 2016 261 D. Seargent, Weird Astronomical Theories of the Solar System and Beyond, Astronomers’ Universe, DOI 10.1007/978-3-319-25295-7 262 Appendix B: The Sutter’s Mill Meteorite… prior to its encounter with Earth, consistent with having been an early- arriving member of this shower. The immediate parent of the southern Taurids is considered to be Comet Encke. Presumably, this comet is also the immediate parent of, at least, the more northerly members of the May Arietids. If that is correct, it seems that a good case can be made for identifying this meteorite as also being a fragment of Comet Encke. Author Index A Crick, F. , 6 Alfven, H. , 64–68 , 70 , 168 , 169 , 208 Crommelin, A.C.D , 45 , 146 , 147 Alvarez, L. , 109 Alvarez, W. , 106 , 109 Anaxagoras , 2 D Anders, E. , 27 , 28 Davis, M. , 119 Anderson, P. , 3 , 232 Deamer, D. , 12 Aristotle , 215 , 216 , 232 De Duiller, N.F. , 84 , 85 Arrhenius, S. , 2 , 3 , 66 , 67 Diogenes , 217 , 222 , 223 Ashby, D. , 172 Dirac, P. , 211 Asher, D. , 30 Dobson, J. , 101 Doniela , 232 , 233 , 235 , 237–240 Drummond, J. , 37–39 B Druyan, A. , 197 , 198 , 201 Bakker, R. , 111 Bambach, R. , 118 , 120 Barabanov, S. , 44 E Beech, M. , 171 Einstein, A. , 64 , 99 , 100 , 103 , 104 , 254 Beech, P. , 39 Everett, H. , 228–230 Benner, S. , 15 Berzelius, J. , 2 Bessel, F.

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