One of the research themes of CLEVER Planets is how life-essential elements are delivered to planets. One source of delivery is the bombardment, or late accretion phase. A study involving CLEVER Planets researchers Andre Izidoro and Rajdeep Dasgupta was published today in Nature Astronomy, exploring late accretion in the TRAPPIST-1 exoplanet system.
TRAPPIST-1 is a small, ultra-cool star located 39 light years away, hosting seven Earth-sized planets that orbit the star in a near-perfect harmony. The investigators used this fragile orbital balance to place an upper limit on how much bombardment the planets could have tolerated in their infancy.
Resonant orbital structures form when young planets migrate close to the host star before the protoplanetary disk dissipates, within the first few million years since formation, but can be easily disrupted by impacts during late accretion. Through modeling, the investigators determined that TRAPPIST-1’s current resonant structure could not have survived if the planets were bombarded by more than 5% of one Earth mass.
The implication of this result is that the TRAPPIST-1 planets formed very early in the life of the system, relative to Earth’s formation within the solar system. CLEVER Planets researcher Izidoro says:
“For the TRAPPIST-1 system, we have these Earth-mass planets that formed early. So one potential difference, compared to the Earth’s formation, is that they could have, from the beginning, some hydrogen atmosphere and have never experienced a late giant impact. And this might change a lot of the evolution in terms of the interior of the planet, outgassing, volatile loss and other things that have implications for habitability.”
Read more about the study in the official Rice University press release, or check out the full paper in Nature Astronomy.
Image credit: NASA/JPL-Caltech