That's interesting you should mention this, as during lunch I watched a History Chanel (I think) program on this effect. Supposedly the Earth was either nearly or entirely frozen during two or three periods in its past, either delaying or preventing the early establishment of multicellular life, but also as recently as 850 to 635 mya, during the Cryogenian period, during which the Sturtian and Marinoan glaciations occurred, the greatest ice ages known for Earth.

Of course we've had ice age temperatures considerably warmer than today, including 400 tya, 325 tya, 245 tya, and 120 tya. Beyond that, the ice core samples are unavailable, but other means, such as compilations of oxygen isotope measurements on benthic foraminifera strongly indicate that the Earth was much warmer throughout most of its history (2 to 12 deg C, mean around 6 deg C) than it is today.

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If I set the budget, we'd have Ares and more. Unfortunately, I don't set the budget, and Ares is just too expensive and too far out for us to accomplish our goals within the budget we were given.

If we halt the ISS, all versions of Ares, and transport Orion and Altair aboard DIRECTv3's Jupiter family of Shuttle-Derived Launch Vehicles, we just might make it back to the Moon by 2020.