Readers have questions about Ultima Thule, thirsty plants and vitamin D

Your letters and comments on the February 2, 2019 issue of Science News

Which way is up?

Initial observations of the Kuiper Belt object MU69, nicknamed Ultima Thule, suggested it had a snowmanlike shape. Ultima Thule’s two lobes are connected by a narrow neck that appears brighter than the rest of the space rock’s surface, Lisa Grossman reported in “New Horizons shows Ultima Thule looks like a snowman, or maybe BB-8” (SN: 2/2/19, p.