Earth’s Mini-Moons

Granvik, Vaubaillon & Jedicke, 2012 Abstract Confusion

? Searching for Main Belt Comets (water) in the Main Belt Sonnet, Kleyna, Jedicke & Masiero, 2011

Elst-Pizzaro image courtesy of H. Hsieh. Results ZERO Goals • identify new main belt comets • measure the MBC:MBA ratio • locate the contemporary snow line TALCS (Masiero et al. 2009)

• Thousand Asteroid Light Curve Survey – 924 asteroids – 80% with >40 detections Two Techniques • Identify coma – target `fuzziness’ • Identify tails – directed flux near target PSFtarget = fnucleus PSFnucleus + fcoma PSFcoma

fnucleus + fcoma =1

Searching€ for Coma Derived Mass Loss Rates

sensitivity (99.9% CL) 0.2 kg/s

known MBCs Searching for Tails

Elst-Pizzaro image courtesy of H. Hsieh. brightest pie segment Tail Test orientation detections null hypothesis

brightest segment rank order relative to stars Tail Detection Significance

null hypothesis

5% of asteroids σ Tail Direction Significance position angle angle position

anti-solar enhancement? w.r.t . anti-solar . anti-solar Earth’s Mini-Moons

Granvik, Vaubaillon & Jedicke, 2012 Jovian Natural Satellites

Jupiter

Jupiter Earth’s Other Natural Satellites? ? Why Study Mini-Moons?

• provide strong constraints on Near Earth Object models • intermediate source population for some meteoroids/meteorites • natural space debris • perfect targets for sample return mission Early Work on Earth’s Mini-Moons • Denning (1916): – ‘the large meteors that passed over Northern America on February 9, 1913, must have been temporary Earth satellites’ because the orbits were ‘concentric, or nearly concentric, with the Earth's surface.’ • Baker (1958): – artifical satellites ‘may be accompanied in their journey through space by certain “natural" satellites.’ • Cassidy et al. (1965): – suggested craters in Argentina and Chile were caused by a mini-moon on a decaying orbit • Cline (1979): – analytical results suggest a possible capture mechanism via a very close encounter with the Moon • Namouni et al. (1999): – simulations suggest a possibility for a NES population on retrograde orbits • 1991 VG (Tancredi 1997) and 2006 RH120 (Kwiatkowski et al. 2009): – the first mini-moons Other Work on Irregular Satellites 2006 RH120 Earth’s first known irregular satellite Mini-Moon Source Population Generating NEO mini-moon Candidates • a, e, i, randomly selected from NEO populaon • random angular elements ( Ω, ω, M ) from flat distribuon • random epoch within 19-year Metonic Cycle

Earth’s Hill sphere (0.01 AU) Generating NEO mini-moon Candidates • a, e, i, randomly selected from NEO populaon • random angular elements ( Ω, ω, M ) from flat distribuon • random epoch within 19-year Metonic Cycle • 0.04 AU < Δ < 0.05 AU

Earth’s Hill sphere (0.01 AU) Generating NEO mini-moon Candidates • a, e, i, randomly selected from NEO populaon • random angular elements ( Ω, ω, M ) from flat distribuon • random epoch within 19-year Metonic Cycle • 0.04 AU < Δ < 0.05 AU • vEarth < 3 km/s Earth’s Hill sphere (0.01 AU) Generating NEO mini-moon Candidates • a, e, i, randomly selected from NEO populaon • random angular elements ( Ω, ω, M ) from flat distribuon • random epoch within 19-year Metonic Cycle • 0.04 AU < Δ < 0.05 AU • vEarth < 3 km/s • Direcon angle < 120 deg Earth’s Hill sphere (0.01 AU) Generating NEO mini-moon Candidates

Earth’s Hill sphere • 10 10 generated NEOs (0.01 AU) Generating NEO mini-moon Candidates

Earth’s Hill sphere • 10 10 generated NEOs (0.01 AU) • 10 7 met criteria and were integrated Generating NEO mini-moon Candidates

Earth’s Hill sphere • 10 10 generated NEOs (0.01 AU) • 10 7 met criteria and were integrated • 16,000 were ‘captured’ Capture Definition

Ekinec + Epotenal < 0

within the hill sphere mini-moon ‘Orbits’ mini-moon ‘Orbits’ mini-moon ‘Orbits’ mini-moon ‘Orbits’ NEO MODEL

approach earth @ aphelion approach earth @ perihelion

dangerous objects mini-moon capture region Mini-moon Capture Probability Mini-Moon Capture Orientation

L1 to sun Mini-moon Geocentric Orbit Distribuon

Earth’s Hill Sphere Radius Mini-moon Geocentric Orbit Distribuon

Earth’s Hill Sphere Radius

long-lived capture inside the moon’s orbit Mini-moon Lifemes

long-lived captures dominate residence mes Mini-moon lifeme (years) How many Mini-Moons are there? Mini-moon diameter (meters) Average me between mini-moons (years)

# of mini-moons

Boke et al 2002 2006 RH120 Number of steady state mini-moons How many Mini-Moons are there? 2 How many Mini-Moons are there? Mini-moon Sky-Plane Distribuon A STEROID

ERRESTRIAL TIMPACT L AST

A LERT

SYSTEM Mini- Summaries • ZERO main belt comets • measured MBC:MBA ratios (m>0.2kg/s)  – 1:300 – inner belt (H<21) – 1:350 – middle belt (H<19.5) – 1:500 – outer belt (H<18) • low S/N detection of tails for 5% of main belt asteroids

• MANY mini-moons • 1-2 one-meter diameter mini-moons at any time Creating the PSFs

TALCS image Creating the PSFs single target image Creating the PSFs

Target PSF

multiple images median stacked Creating the PSFs

Target PSF

multiple nearby field stars trailed

& median stacked Creating the PSFs

Target PSF

Nuclear PSF multiple trailed field stars median stacked

Creating the PSFs

Target PSF

Coma PSF Nuclear PSF

Nuclear PSF convolved with 1/r symmetric coma

Creating the PSFs

Target PSF

Coma PSF Nuclear PSF Creating the PSFs

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