Terrestrial Planet Formation in Disks with Varying Surface Density Profiles

The ``minimum-mass solar nebula'' (MMSN) model estimates the surface densitydistribution of the protoplanetary disk by assuming the planets to have formedin situ. However, significant radial migration of the giant planets likelyoccurred in the Solar system, implying a distortion in the values derived bythe MMSN method. The true density profiles of protoplanetary disks is thereforeuncertain. Here we present results of simulations of late-stage terrestrialaccretion, each starting from a disk of planetary embryos. We assume apower-law surface density profile that varies with heliocentric distance r asr^-alpha, and vary alpha between 1/2 and 5/2 (alpha = 3/2 for the MMSN model).We find that for steeper profiles (higher values of alpha), the terrestrialplanets (i) are more numerous, (ii) form more quickly, (iii) form closer to thestar, (iv) are more massive, (v) have higher iron contents, and (vi) have lowerwater contents. However, the possibility of forming potentially habitableplanets does not appear to vary strongly with alpha.Comment: 10 pages, 5 figures in emulateapj style. tp appear in Oct 20, 2005, issue of Ap