I’ve been thinking about how useful objects in our own Solar System are when we compare them to other stellar systems. Our situation has its idiosyncrasies and certainly does not represent a standard way for planetary systems to form. But we can learn a lot about what is happening at places like Beta Pictoris by studying what we can work out about the Sun’s protoplanetary disk and the factors that shaped it. Illumination can come about in both directions.
Think about that famous Voyager photograph of Earth, now the subject of an interesting new book by Jon Willis called The Pale Blue Data Point (Princeton, 2025). I’m working on this one and am not yet ready to review it, but when I do I’ll surely be discussing how the best we can do at studying a living terrestrial planet at a considerable distance is our own planet from 6 billion kilometers. We’ll use studies of the pale blue dot to inform our work with new instrumentation as we begin to resolve planets of the terrestrial kind.
But let’s look much further out, and a great deal further back in time. A 2003 detection at Beta Pictoris led eventually to confirmation of a planet in the early stages of formation there. Probing how exoplanets form is an ongoing task stuffed with questions and sparkling with new observations. As with every other aspect of exoplanet research, things are moving quickly in this area. Perhaps 25 million years old, this system offers information about the mechanisms involved in the early days of our own. Here on Earth, we also get the benefit of meteorites delivering ancient material for our inspection.
The role of Jupiter in shaping the protoplanetary disk is hard to miss. We’re beginning to learn that planetesimals, which are considered the building blocks of planets, did not form simultaneously around the Sun, and the mechanisms now coming into view affect any budding planetary system. In new work out of Rice University, senior author André Izidoro and graduate student Baibhav Srivastava have gone to work on dust evolution and planet formation using computer simulations that analyze the isotopic variation among meteorites as clues to a process that may be partially preserved in carbonaceous chondrites.
Image: Enhanced image of Jupiter by Kevin M. Gill (CC-BY) based on images provided courtesy of NASA/JPL-Caltech/SwRI/MSSS (Credit: NASA).
The authors posit that dense bands of planetesimals, created by the gravitational effects of the early-forming Jupiter, were but the second generation of such objects in the system’s history. The earlier generation, whose survivors are noncarbonaceous (NC) magmatic iron meteorites, seems to have formed within the first million years. Some two to three million years would pass before the chondrites formed, containing within themselves calcium-aluminum–rich inclusions from that earlier time. The rounded grains called ‘chrondules’ contain once molten silicates that help to preserve that era.
The key fact: Meteorites from objects that formed during the first generation of planetesimal formation melted and differentiated, making retrieval of their original composition problematic. Chondrites, which formed later, better preserve dust from the early Solar System and also contain distinctive ‘chondrules,’ which solidified after going through an early molten state. But the very presence of this isotopic variation demands explanation. From the paper:
…the late accretion of a planetesimal population does not appear readily compatible with a key feature of the Solar System: its isotopic dichotomy. This dichotomy—between NC and carbonaceous (CC) meteorites —is typically attributed to an early and persistent separation between inner and outer disk reservoirs, established by the formation of Jupiter or a pressure bump. In this framework, Jupiter (or a pressure bump) acts as a barrier that prevents the inward drift of pebbles from the outer disk and mixing, preserving isotopic distinctiveness.
But this ‘barrier’ would also seem to prevent small solids moving inwards to the inner disk, so the question becomes, how did enough material remain to allow the formation of early planetesimals at the later era of the chondrites? What is needed is a way to ‘re-stock’ this reservoir of material. Hence this paper. The authors hypothesize a ‘replenished reservoir’ of inner disk materials gravitationally gathered in the gaps in the disk opened up by Jupiter. The accretion of the chondrites and the locations where the terrestrial planets formed are interconnected as the early disk is shaped by the gas giant.
André Izidoro (Rice University) is senior author of the paper:
“Chondrites are like time capsules from the dawn of the solar system. They have fallen to Earth over billions of years, where scientists collect and study them to unlock clues about our cosmic origins. The mystery has always been: Why did some of these meteorites form so late, 2 to 3 million years after the first solids? Our results show that Jupiter itself created the conditions for their delayed birth.”
Image: This is Figure 1 from the paper. Caption: Schematic illustration of the proposed evolutionary scenario for the early inner Solar System over the first ~3 Myr. (A) At early times (t ~ 0.1 Myr), radial drift and turbulent mixing transport dust grains across the disk. (B) Around ≲ 0.t to 1 Myr, primordial planetesimal formation occurs in rings. (C) By ~1.5 Myr, growing planetary embryos start to migrate inward under the influence of the gaseous protoplanetary disk, whereas Jupiter’s core enters rapid gas accretion phase. (D) Around ~2 Myr, Jupiter’s gravitational perturbations excite spiral density waves, inducing pressure bumps in the inner disk. Giant impacts among migrating embryos generate additional debris. Pressure bumps act as dust traps, halting inward drift of small solids and leading to dust accumulation. (E) Between ~2 and 3 Myr, dust accumulation at pressure bumps leads to the formation of a second generation of planetesimals. Rapid gas depletion in the inner disk, combined with the presence of these traps, limits the inward migration of growing embryos. (F) By ~3 Myr, the inner gas disk is largely dissipated, resulting in a system composed of terrestrial embryos and a second generation of planetesimals—potentially the parent bodies of ordinary and enstatite chondrites—whereas the inner disk evolves into a gas-depleted cavity.
A separation between material from the outer Solar System and the inner regions preserved the distinctive isotopic signatures in the two populations. Opening up this gap, according to the authors, enabled regions where new planetesimals could grow into rocky worlds. Meanwhile, the presence of the gas giant also prevented the flow of gaseous materials toward the inner system, suppressing what might have been migration of young planets like ours toward the Sun. These are helpful simulations in that they sketch a way for planetesimals to form without being drawn into our star, but there are broad issues that remain unanswered here, as the paper acknowledges:
Our simulations demonstrate that Jupiter’s induced rapid inner gaseous disk depletion, gaps, and rings are broadly consistent with both the birthplaces of the terrestrial planets and the accretion ages of the parent bodies of NC chondrites. Our results suggest that Jupiter formed early, within ~1.5 to 2 Myr of the Solar System’s onset, and strongly influenced the inner disk evolution….
And here is reason for caution:
…we…neglect the effects of Jupiter’s gas-driven migration. This simplification is motivated by the fact that, once Jupiter opens a deep gap in a low-viscosity disk, its migration is expected to be fairly slow, particularly as the inner disk becomes depleted. Simulations show that, in low-viscosity disks, migration can be halted or reversed depending on the local disk structure. In reality, Jupiter probably formed beyond the initial position assumed in our simulations and first migrated via type I migration and eventually entered in the type II regime… but its exact migration history is difficult to constrain.
The authors thus guide the direction of future research into further consideration of Jupiter’s migration and its effects upon disk dynamics. Continuing study of young disks like that afforded by the Atacama Large Millimeter/submillimeter Array (ALMA) and other telescopes will help to clarify the ways in which disks can spawn first gas giants and then rocky worlds.
The paper is Srivastava & Izidoro, “The late formation of chondrites as a consequence of Jupiter-induced gaps and rings,” Science Advances Vol. 11, No. 43 (22 October 2025). Full text.
