Asteroids and comets are some of the most dangerous things in the universe when it comes to the safety of Earth as a planet, which is why NASA has set up programs such as CNEOS or the Center for Near Earth Object Studies.
CNEOS is designed to be a ledger of all of the discovered near-Earth objects, providing a database on all of their orbits, locations, speeds, rotational speeds, and any other relevant information about the object. Programs such as this and others are set up because of the real danger these objects pose, and the most unsettling aspect of these objects is we don't know where they all are.
It was only in October last year NASA took to its website to share the infographic below about how many asteroids it estimates it has yet to discover. Now, a new study published on a pre-print server has detailed what is called "dark comets," which are icy objects just like normal comets, but instead, they do not exhibit any outgassing, which causes the iconic tail depicted in traditional comets.
The lack of outgassing means these comets are much harder to spot, as astronomers typically discover comets by identifying light reflecting off the molecules within the plumes of gas expelling off the comet's body. Instead of outgassing, these dark comets exhibit some kind of "nongravitational acceleration", which has led researchers to believe there is some kind of other force pushing them throughout their unique orbits.
To overcome this issue, NASA and other space agencies need to implement programs dedicated to the discovery of rogue objects such as comets, dark comets, and even asteroids.