Passage I

Io, one of Jupiter's moons, was studied with 2 spacecraft instruments that can detect visible radiation or thermal infrared (TIR) radiation (sec Table 1).

The instruments located volcanic regions called hot spots on Io. Hot spots are areas where molten material at or above 400 K is ejected. Three studies of Io's hot spots were performed.

Study 1

The instrument on the spacecraft orbiting Io recorded the locations of all hot spots. Figure 1 show the latitudes of those hot spots in both hemispheres.

Study 2

The intensity of the of emitted radiation from each hot spot was used to estimate the hot spot's area and average temperature. The hot spots were grouped into 2 categories: Type Ⅰ hot spots having average temperatures below 500 K and Type Ⅱ hot spots having average temperatures above 500 K. Type II hot spots emit higher intensity radiation than do Type l hot spots. The results for 10 hot spots are shown in Table 2.

Study 3

Scientists believe that each of Io's hot spots ejects 1 of 3 types of molten material: molten sulfur, material similar in composition to basalt lava, or material similar in composition to ultramafic lava. Basalt lava and ultramafic lava have been ejected from Earth's volcanoes. Table 3 gives the melting point of sulfur and the 2 types of lava, and the boiling point of sulfur, all at a pressure of 1 atmo­sphere (atm).