Inti didn’t form in the X wind(and neither did most CAIs)

Steve DeschArizona State University

Harold Connolly, Jr.CUNY Kingsborough

Outline of Talk

• Diving into Inti

• Inti didn’t form in an X-wind...

• ...but it ended up in a comet anyway, because...

Inti Introduced

Comet 81P/Wild 2Scattered into present orbit in 1974; was previously a member of the Kuiper Belt Scattered Disk

Probably formed at 10-30 AU

Stardust Sample Track 25 called ‘Inti’. It’s a CAI, formed (by condensation) at > 1700 K.

Zolensky et al (2006)

X-wind windicated? Shu et al. (1996, 2001)

rockvapor ~ 10-12 g cm-3

1. Gas (H2), small (< 100 um) solids rapidly funneled away from CAI-forming zone

gas(H+) ~ 10-16 g cm-3

3. CAIs grow by evaporation / recondensation here

2. Large (> 100 um) “proto-CAIs” enter Reconnection Ring

4. CAIs flung by X-wind into comets.

X-wind = eXtra-oXidizing Gas in reconnection ring ionized, funneled onto star.

Shu et al. (2001) estimate (from protostellar X-ray emission) T= 8 x 106 K, ne = 108 cm-3 (gas ~ 10-16 g cm-3) between flares, in reconnection ring.

CAIs grow in reconnection ring by re-condensation following flares, from rock vapor (rockvapor ~ 10-12 g cm-3)

Fedkin & Grossman (2006)

Intrinsic fO2 of CAI vapor > IW+1 (Kozul et al. 1988)

CAIs form in reconnection ring, where fO2 ~ 106 x solar, near IW

Inti Revealed

Inti itself is small, < 10 microns

Inti contains within its spinel grains of osbornite, (Ti,V)N (likely condensates).

Redox ReduxfO2 during CAI formation known to be < IW-6 from Ti4+/Ti3+ ratios in fassaite and rhönite (Beckett 1986,

Krot et al. 2000)

Osbornite in Inti shows it also formed in the gas of the solar nebula!

Osbornite-bearing CAI recently found in CH/CB Isheyevo, recognized as formed in the solar nebula (Meibom et al. 2007), demands C/O = 0.91-0.94 (IW-7) (Ebel 2006)

Solar nebula ebb and flow

r (AU) 5 10 15 20 25 30

‘Nice model’ (Tsiganis et al. 2005; Gomes et al. 2005): the outer planets formed much closer to Sun

Minimum mass solar nebula (Weidenschilling 1977), with (r) r^(-1.50), must be updated!

Desch (2007) shows (r) r^(-2.17) !

Outer Solar Nebula = Decretion DiskAll viscously evolving disks viscously spread outward.

Mass distribution can be matched by a spreading disk, with outward mass flow (Desch 2007).

Steady-state solution with outward mass flow also matches (Desch 2007.) If (r) r^(-p) and T(r) r^(-q), mass must flow outwards if p+q > 2 (Takeuchi & Lin 2002)

Gas, CAIs moved from a few AU to > 10 AU in < 10 Myr

Desch (2007, in revision)

Conclusions•X-wind predicts fO2 where CAIs formed > IW. But CAIs overall formed in solar gas, < IW-6 (rhönite / fassaite), and Inti in particular at IW-7 (osbornite).

•Inti too small to enter reconnection ring as a proto-CAI; probably too small even to be ejected by X-wind.

•Nice model for initial planet positions used by Desch (2007) to derive new “minimum mass solar nebula”. Derived density profile so steep, mass must have flowed outward, from a few AU to > 10 AU in < 10 Myr.

•Inti (like all CAIs) formed in the solar nebula; it was transported by disk dynamics to comet-forming zone.