“Why us? And why Earth?”: a planetologist’s fascination with celestial bodies
Paolo Sossi is fascinated by how celestial bodies form. Even so, he would think twice before embarking on a journey to another planet.?
What makes you so interested in the formation of planets?
Paolo Sossi: I’m endlessly intrigued by how planets came to be, as it’s a question that has profoundly influenced human history and thought over the centuries. Celestial bodies helped Galileo Galilei shape the Renaissance and served as the in?spiration for Newton’s laws. So, it’s only natural to wonder: Why us? And why Earth?
Knowledge with global reach
What’s your most significant discovery?
That Earth and Venus formed in the same way – shrouded in a dense, suffocating atmosphere rich in carbon dioxide. Both planets probably had magma oceans when they first formed. In the lab, we created a miniature Earth by using a laser to produce a ball of lava. Gases that may have existed on the early Earth kept the ball suspended in mid-air. By comparing the composition of our mini-Earth with rocks from Earth’s mantle today, we were able to show that the early Earth had an atmosphere consisting mainly of CO? and nitrogen in the same proportions and at the same pressures as on Venus today.
What’s your favourite terrestrial planet?
I have a love-hate relationship with 55 Cancri e. The planet has about 8 times Earth’s mass but is 25 times closer to its sun than Mercury is to ours. That means its surface temperature is over 2,000 degrees Celsius – hot enough to melt most rocks. And though it is relatively close to us and easy to observe, the spectroscopic measurements of its atmosphere are so variable that we can’t work out what it’s made of.
If you had the chance, would you travel to another planet?
I’d have to weigh the sheer thrill of setting foot on another planet against the likelihood of not being able to return to Earth. Here and now, it’s easy to say I’d go, because I know the technology doesn’t exist! But if I were actually offered the chance to travel to 55 Cancri e, for instance, I’m not so sure I would take it.