The whole history of human existence is a small blip in the 4.5-billion-year history of our solar system. Before settling in their present configuration, no one was around to see planets forming and undergoing dramatic changes. Scientists need to hunt for clues to that mysterious distant past in order to understand what came before us -before life on Earth and before Earth itself.
NASA has a long history of exploring small bodies, beginning with Galileo’s 1991 flyby of asteroid Gaspra. The first spacecraft to orbit an asteroid, Near Earth Asteroid Rendezvous (NEAR) Shoemaker, also successfully landed on asteroid Eros in 2000 and took measurements that originally hadn’t been planned. The Deep Impact mission drove a probe into Comet Tempel 1 in 2005 and prompted scientists to rethink where comets formed. More recent efforts have built on those successes and will continue to teach us more about our solar system.
Building Blocks of Planets
Our solar system, as we know it today, is formed from dust grains-tiny rock, metal and ice particles-swirling around our infant Sun in a disk. Most of the material from this disk fell into the newborn star, but some bits avoided this fate and stuck together, growing into asteroids, comets and even planets. To this day, many of the remains of that process have survived. Planetary growth from smaller objects is one piece of our history that can help us investigate asteroids and comets.
Artist’s impression of the 2014 MU69 spacecraft of NASA’s New Horizons, a Kuiper Belt object orbiting the Sun 1 billion miles (1.6 billion kilometers) beyond Pluto on January 1, 2019.
Delivery of the Elements of Life
It is also likely that small worlds are responsible for seeding Earth with the life ingredients. Studying how much water they have is evidence of how they helped seed life on Earth.”Small bodies are the game changers. They participate in the slow and steady evolution of our solar system over time and influence planetary atmospheres and life opportunities.
This “super – resolution” view of Ben-nu asteroid was created using eight images from a distance of approximately 205 miles (330 kilometers) from NASA’s OSIRIS – Rex spacecraft on Oct. 29, 2018.
Tracers of Solar System Evolution
Between 50 and 500 million years after the Sun formed, a particularly catastrophic time for the solar system. The objects around them were reorganized by Jupiter and Saturn, the most massive giants of our system, as their gravity interacted with smaller worlds like asteroids.
As Jupiter and Saturn moved around, Uranus and Neptune may have originated closer to the Sun and kicked outward. Indeed, Saturn may have prevented Jupiter from “eating” some of the earth’s planets, including Earth, as its gravity counteracted the further movement of Jupiter toward the Sun.
Processes in an Evolving Solar System
You may notice scattered sunlight in the ecliptic plane, the region of the sky where the planets orbit, after sunset, under the right conditions. This is because dust from the collisions of small bodies such as comets and asteroids scatters sunlight. Scientists refer to this phenomenon as “zodiac light,” and this is an indication that our solar system is still active. Around other stars, zodiacal dust indicates that they too can harbor active planetary systems.
Hazards to Earth
While the Trojans are stuck being Jupiter groupies, Ben-nu, the target of the OSIRIS-Rex mission, is one of the most potentially hazardous asteroids to Earth that is currently known, even though its odds of colliding with Earth are still relatively small; scientists estimate Ben-nu has a 1‐in‐2,700 chance of impacting our planet during one of its close approaches to Earth in the late 22nd century. Right now, scientists can predict Ben nu’s path quite precisely through the year 2135, when the asteroid will make one of its close passes by Earth.
Small Worlds as Pit Stops, Resources for Future Exploration
There are no gas stations in space yet, but scientists and engineers are already beginning to think about how asteroids might one day serve as spacecraft refueling stations on the way to more distant destinations. These small worlds could help astronauts restore their supplies as well. Ben-nu For example, is likely to have water bound in clay minerals that might one day be harvested to hydrate thirsty space travelers.
They are small worlds, after all.