Summary
Highlights
In 2016, Juno arrived at Jupiter, providing the closest views ever of the gas giant. Its mission aimed to probe Jupiter's interior. Using gravity variations, Juno mapped the planet's heart, discovering an amorphous, 'fuzzy' core—a mixture of hydrogen, rocky material, and pebbles, challenging previous models of planetary formation. This suggests Jupiter may have formed from tiny pebbles and swallowed other planet cores, dissolving them into its own.
Sending spacecraft to Jupiter is challenging due to distance and speed. Landing on Mars is even more difficult, with only a 50% success rate, due to its thin atmosphere. This thin atmosphere, 100 times thinner than Earth's, is a result of Mars lacking a magnetic field to protect it from solar wind after its core cooled early in its history. New landing techniques are being developed, including gliding through the atmosphere, but dust storms remain a major hazard.
Jupiter needed to form rapidly, within 4-5 million years, before the young sun blew away the protoplanetary disk. The 'pebble accretion' theory suggests that protoplanets can grow much faster by feeding on surrounding centimeter-sized pebbles. This efficient growth allowed Jupiter to form its large rocky core quickly, enabling it to gobble up surrounding gas and become the giant planet we see today.
Many exoplanets, including the WASP planets, orbit extremely close to their stars, a region where they shouldn't be able to form. This phenomenon is explained by planetary migration, where giant planets form further out in gas-rich disks and are then pushed inwards towards their host stars by the significant gravitational forces within the disk.
Earth's orbit around the sun is not perfectly circular and changes over time, influencing our climate and triggering ice ages. Jupiter, being the solar system's largest planet, along with Venus, gravitationally tugs on Earth's orbit every 405,000 years, stretching it into a greater ellipse. This causes more extreme temperature variations on Earth, highlighting Jupiter's role in our planet's climatic cycles.
The solar system's journey around the Milky Way is not a flat orbit; it bobs up and down through the galactic plane every 60,000 years. This motion exposes Earth to different galactic environments, which some research suggests could be linked to past extinction events, such as the series of events that wiped out 95% of species over 3.7 billion years.
Maps of the Moon's surface reveal ancient lava seas, formed by massive volcanic eruptions billions of years ago. These eruptions spewed out vast amounts of gas, including water vapor, potentially creating a thin atmosphere around the moon capable of sustaining liquid water on its surface for millions of years. This raises the plausible, though unconfirmed, possibility of a habitable period on the moon.
Re-examination of Apollo 15 lunar rocks revealed evidence of a magnetic field on the moon a billion years ago, much later than expected. This challenges previous assumptions about the moon's rapid cooling. Additionally, mysterious dense regions deep within Earth's mantle, dating back 4.5 billion years, are believed to be remnants of Theia, the protoplanet that collided with Earth. This collision formed the moon and gave Earth a larger iron core, which is crucial for our planet's protective magnetic field and stable climate.
Saturn's diverse moon system suggests a violent past, with some moons forming with the planet and others captured during a solar system upheaval. Titan, Saturn's largest moon, grew by gorging on debris from these collisions, developing a dense atmosphere. This atmosphere allows for methane-based rain, rivers, and lakes, making it a unique, Earth-like world. While extremely cold, the presence of vinyl cyanide suggests a potential for 'alien' life forms with cell membranes different from Earth's water-based life.