A planetary mass the size of Mars could be warping the orbits of some smaller objects beyond Neptune.

Just as fossils provide a record of ancient life on Earth, objects at the edge of our solar system offer clues about how our planetary system formed and developed.

“It’s the attic of our solar system,” planetary sciences professor Renu Malhotra says of the vast space beyond Neptune and Pluto, where researchers think there could be more planets.

The bodies out there hold historical and evolutionary information about the solar system. Quite a few have been observed, but what Malhotra and her team are searching for are bigger objects. “The outer solar system is a frontier,” she says. The icy bodies in the Kuiper Belt were first discovered about 25 years ago. That belt extends at least twice as far as Neptune is from Earth, doubling the size of the solar system.

“There are things we can learn from studying samples in the laboratory, and there is lots we can learn from studying the distribution of small bodies beyond Neptune,” Malhotra says.


Renu Malhotra is a Regents’ Professor of planetary sciences; the Louise Foucar Marshall Science Research professor; member of the National Academy of Sciences; and fellow of the American Academy of Arts and Sciences.

Malhotra is excited to study the way these distant small objects are distributed, and that their orbital parameters provide “hints of the imprint of the gravity of bigger objects, planet-sized, that we haven’t yet discovered.” She says she has spent sleepless nights calculating “how we could use the little bits of evidence we have in the spatial structure of these small bodies to ferret out where unseen planets might be located and find them.”