1. 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.
DPS 49 ● Provo, Utah ● Oct 18, 2017

2. ● Population control of Martian Trojans ●
Apostolos Christou
DPS ● 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

3. ● Population control of Martian Trojans ●
Apostolos Christou
DPS ● Provo, Utah ● Oct 18, 2017
(5261 )
Eureka
( ) VF31
( ) 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

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

5. 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.
Cerro Tololo
VF 31

6. ● Population control of Martian Trojans ●
Apostolos Christou
DPS ● 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

7. ● Population control of Martian Trojans ●
Apostolos Christou
DPS ● 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

8. ● Population control of Martian Trojans ●
Apostolos Christou
DPS ● 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

9. ● Population control of Martian Trojans ●
Apostolos Christou
DPS ● Provo, Utah ● Oct 18, 2017
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)