Finding the building blocks of life a billion miles beyond Pluto

Try for a moment to wrap your mind around the concept of “deep time.” That is, a time long ago when the dinosaurs lived, or when our planet came to be, about 4.5 billion years ago. So much has happened since that time that the Earth, Moon, sun and, in fact, our entire solar system has changed dramatically.

How do we study such long-ago events? It is possible, but not easy. 

The challenge is to find objects that clue us in to what happened long ago in deep time. There are very few rocks that date to more than 3 billion years on Earth, and none that date to when the Earth formed. But objects that have not changed in 4.5 billion years do exist. One is Ultima Thule — the Kuiper Belt Object that the New Horizons spacecraft flew by in January.

Ultima Thule is believed to be a remnant of the formation of our solar system. What’s more, because of Ultima Thule’s location in the distant solar system — a billion miles beyond Pluto and, obviously even farther from our sun — it has not changed since it formed.

In other words, Ultima Thule is an unchanged piece of debris left over from the formation of the solar system. When the planets formed their gravity swept up everything around them except for a few pieces that were somehow missed or were ejected outward. So, when we study Ultima Thule, we are, in fact, studying the kind of objects that came together 4.5 billion years ago to form the planets. As such, Ultima Thule contains a wealth of information about what our solar system was made from, how the solar system formed, and in particular how the Earth itself came to be what it is today.

As we have found, it also could contain the building blocks of life — water, carbon and energy.

New Horizons passed within 2,200 miles of Ultima Thule. With its instrumentation pointed at the ancient object, what we saw was simply astonishing.

First, Ultima Thule turned out to be a binary object made up of two of the “pieces” that came together to form the planets, but which had somehow stuck together on their edges. Those pieces came together so gently they did not deform each other.

Each piece is different from the other. The smaller one is somewhat like a slightly flattened soccer ball. The other is shaped more like a thick pancake. These shapes are not at all what we were expecting. This is challenging our understanding of the very first steps of how the planets first formed.  

Also, there are bright areas on the surface of Ultima Thule that suggest the presence ices such as water or methane. And there are large reddish areas suggesting the presence of organic molecules. As methane is continuously exposed to the high-energy cosmic radiation, it is chemically changed into such reddish and progressively more carbon-rich substances. This may be telling us that even the first pieces that made the planets already contained water, carbon and energy, the raw materials of life. 

At this point we have received back only a small fraction of the observations made by New Horizons as it passed by Ultima Thule. Because it is about 6 billion miles from Earth, the transmission of data is very slow. It will take about 20 months to get all the date back. No doubt, there are more discoveries waiting in that data. But 20 months is a small amount of time to wait, when we consider that we are getting information about an object that was truly formed in deep time. 

Michael E. Summers is a professor of planetary science and astronomy at George Mason University in Fairfax, Virginia, and member of the NASA/New Horizons science team.