海角大神

NASA鈥檚 New Horizons mission, the first of its kind to explore the Kuiper Belt beyond Neptune, is officially in countdown mode as the mission advances closer to Pluto, preparing for the July 14 flyby. As the mission draws closer to the icy planet, here are three enduring mysteries that scientists hope to solve.

1. What are the mysterious dark spots the size of Missouri made of?

New color photographs released from the mission at the beginning of July revealed a series of dark spots about 300 miles in diameter, something scientists had not seen before. The spots lay near the equator and resemble shapes seen by impact craters and volcanoes, but the New Horizons team is waiting for more detailed photographs to interpret the features.

2. What are 鈥渢he whale,鈥� 鈥渢he donut,鈥� and that bright white spot?

Somewhat blurry images taken from June 27 to July 3 have helped astronomers create a map of the planet in preparation for the upcoming flyby. The images now show an elongated area 1,860 miles (3,000 kilometers) in length, which the team has dubbed 鈥渢he whale.鈥� Immediately next to the whale鈥檚 鈥渉ead鈥� is the brightest region that has been seen on the planet, "the donut." The circular area is about 990 miles (1,600 kilometers) across, and could be a bright coating created from frozen methane, nitrogen and/or carbon monoxide as NASA鈥檚 New Horizons mission update suggests.

鈥業t鈥檚 easy to imagine you鈥檙e seeing familiar shapes in this bizarre collection of light and dark features. However, it鈥檚 too early to know what these features really are.鈥� said John Spencer of the Southwest Research Institute, Boulder, Colorado, deputy leader of the Geology, Geophysics and Imaging team to NASA.

3. How big is Pluto鈥檚 atmosphere?

The 鈥渙uter limit鈥� of Pluto鈥檚 atmosphere is hard to measure because it may be completely different from Earth鈥檚 atmosphere. According to Michael Summer, a New Horizon鈥檚 co-investigator, 鈥淚f one defines it similar to the way we define the exobase of Earth鈥檚 atmosphere, then Pluto鈥檚 atmosphere has an outer limit of at least seven times Pluto鈥檚 radius above it surface. This means that the volume of Pluto鈥檚 atmosphere is over 350 times the volume of Pluto itself!鈥� Currently, scientists are uncertain about the size of the atmosphere of the frigid planet, and hope to solve the mystery on this mission.

The New Horizons mission is the first of its kind to explore the icy bodies that are found mostly in the Kuiper Belt beyond Neptune. It is believed that these planets reflect what other worlds, including Earth, were like before the planets condensed. Scientists hope to sample the chemical clues locked in these frozen tundras to gain a glimpse of what Earth and other planets were like in their primitive years. Exploration of these types of planets was placed on NASA鈥檚 list of most important missions for this decade, according to the New Horizons press site.

As of Wednesday morning, the New Horizons spacecraft was less than 4.6 million miles from Pluto.