Despite all the information we’ve discovered from our telescopes and outer space missions, there are still many puzzles to solve in our own solar system. Sometimes, it seems the more we learn, the more mysteries we uncover.
1 The Invisible Shield Surrounding Earth
In 1958, James Van Allen from the University of Iowa discovered a pair of radiation belts, an inner and an outer doughnut-shaped ring up to 40,000 kilometers (25,000 mi) above Earth containing high-energy electrons and protons. Earth’s magnetic field holds these radiation belts in place, but they shrink and swell as needed to respond to the Sun’s ejections of energy in our direction.
In 2013, Daniel Baker of the University of Colorado discovered a third structure between the inner and outer Van Allen radiation belts. Baker characterized this structure as a “storage ring” that comes and goes like raising or lowering an invisible shield as needed to block the effect of “killer electrons.” These electrons, which can be dangerous to both astronauts and satellite equipment, dart around Earth at over 16,000 kilometers (100,000 mi) per second when we have severe solar storms.
At an altitude of a little over 11,000 kilometers (7,000 mi), a sharp boundary forms a type of inner edge on the outer radiation belt, blocking these electrons from penetrating deeper into our atmosphere.
“It’s almost like these electrons are running into a glass wall in space,” said Baker. “Somewhat like the shields created by force fields on Star Trek that were used to repel alien weapons, we are seeing an invisible shield blocking these electrons. It’s an extremely puzzling phenomenon.”
Scientists have developed several theories to explain this shield. But so far, none of them work completely.
2 The Flyby Anomaly
Since we started exploring space, our spacecraft have executed flyby maneuvers to use the gravitational energy from a planet or moon to give them a speed boost as they travel into space. These flybys are used on a regular basis to fling satellites deeper into the solar system. But scientists can’t seem to estimate these speeds correctly on a consistent basis. There’s often a tiny, unexplained variation in speed that’s been dubbed the “flyby anomaly.”
We only have the monitoring equipment to detect the precise difference in speeds on flybys of Earth. The anomaly has ranged from a speed decrease of 2 millimeters (0.08 in) per second with NASA’s Cassini in 1999 to a speed boost of 13 millimeters (0.5 in) per second with NASA’s NEAR asteroid spacecraft in 1998.
“These deviations do not seriously affect the trajectories of the spacecrafts,” said Luis Acedo Rodriguez, a physicist at the Polytechnic University of Valencia. “Yet, although they are seemingly small amounts, it is very important to clarify what they are caused by, especially in the current era of precise space exploration.”
Scientists have proposed several causes, from solar radiation to dark matter trapped by our planet’s gravity. But it remains a mystery.