Population Control of Martian Trojans by the Yarkovsky & YORP effects Apostolos Christou Armagh Observatory and Planetarium Northern Ireland, UK My name is Apostolos Christou, work at Armagh Observatory in NI and I am going to talk about a corner of the solar system where asteroids are literally made by sunlight. So, what are trojans. Email: aac@arm.ac.uk DPS 49 ● Provo, Utah ● Oct 18, 2017

● Population control of Martian Trojans ● Apostolos Christou DPS 49 ● Provo, Utah ● Oct 18, 2017 tool depends sensitively on the impactor size distribution, even for a=2.5 it;s 109 yr. so tar will be several 100 Myr, 60o 60o

● Population control of Martian Trojans ● Apostolos Christou DPS 49 ● Provo, Utah ● Oct 18, 2017 (5261 ) Eureka (10142 9) 1998 VF31 (12151 4) 1999 UJ7 tool depends sensitively on the impactor size distribution, even for a=2.5 it;s 109 yr. so tar will be several 100 Myr, 2 km 1 km 0.5 km

● Population control of Martian Trojans ● Apostolos Christou DPS 49 ● Provo, Utah ● Oct 18, 2017 Diagram Brož et al, Proc. IAU Symp., 2006, Fig 6 “YORPlet” (Diagram from Pravec et al, Nature, 2010)

U J7 VF 31 2m @ NAO Rozhen 1m @ Pic du Midi 1.3m @ Cerro Tololo I’ve working in this as part of larger project. That shouldn’t be the case: escaped Trojans, regardless of planet, contribute to the comets or NEO s so you want to know how efficiently that happens; even if orbits don’t change enough to escape, modify the orbit distribution one a few trojans, the only stable asteroids in the terr.planet regon, so somehow related to the early evolution of the terr. planets, just as jupiter trojans related to the giant planets. 1.3m @ Cerro Tololo VF 31

● Population control of Martian Trojans ● Apostolos Christou DPS 49 ● Provo, Utah ● Oct 18, 2017 “Spin Barrier” Eurek a A physical property relevant to YORP is rotation. We know from previous observations that Eureka plots close to the spin barrier. We’ve now observed the other asteroids. VF31 plots further away the most interesting here is UJ7 (the object at L4). It has a 2-day period and this put it into the domain of npa rotators. Now it has been postulated that while asteroids are in this state, YORP becomes ineffective because the torques average out. if tha tis true, this object will be unable to produce YORPlets. VF 31 ? U J7 Tumblers All asteroids

● Population control of Martian Trojans ● Apostolos Christou DPS 49 ● Provo, Utah ● Oct 18, 2017 I’ve working in this as part of larger project. That shouldn’t be the case: escaped Trojans, regardless of planet, contribute to the comets or NEO s so you want to know how efficiently that happens; even if orbits don’t change enough to escape, modify the orbit distribution one a few trojans, the only stable asteroids in the terr.planet regon, so somehow related to the early evolution of the terr. planets, just as jupiter trojans related to the giant planets. VF 31 Eure ka VF 31

● Population control of Martian Trojans ● Apostolos Christou DPS 49 ● Provo, Utah ● Oct 18, 2017 Production (YORP) Loss (Yarkovsky) ✔︎ ✘ = validates the Milani et al conclusion with an analytical argument VF 31 = UJ7 = Eureka Take-Away Message: Radiation forces create but also evict Martian Trojans

● Population control of Martian Trojans ● Apostolos Christou DPS 49 ● Provo, Utah ● Oct 18, 2017 Email: aac@arm.ac.uk Team Members Team Members: Apostolos Christou (Armagh Obs & Plan, UK) Galin Borisov (Armagh Obs & Plan, UK & NAO Rozhen, BG) Seth Jacobson (Northwestern Univ., IL, US) Francois Colas (Obs. Paris, FR) Aldo Dell’Oro (Oss. Arcetri, IT) Alberto Cellino (Oss. Torino, IT) Stefano Bagnulo (Armagh Obs &Plan, UK)