- NASA-backed scientists found Jupiter shaped the distribution of life elements early on
- Nitrogen and phosphorus ratios in meteorites reveal element movement in early solar system
- Iron meteorites came from first planetesimals; chondrites from a later generation
Scientists supported by NASA have uncovered new clues about how Earth may have received some of the key elements needed for life. Their findings suggest that the giant planet Jupiter may have played a much bigger role in shaping the distribution of these elements across the early solar system than previously thought.
The study, published in Science Advances, focuses on two elements that are essential for life as we know it: nitrogen and phosphorus. By examining the ratio of phosphorus to nitrogen in different types of meteorites, researchers traced how these elements moved through the young solar system more than 4.5 billion years ago.
According to the study, the solar system formed from a cloud of gas and dust that swirled around the proto-Sun. This material eventually provided the building blocks for planets, moons and, ultimately, life. Among the many elements present in this cloud, nitrogen and phosphorus were particularly important because they became part of the ingredients needed for living organisms.
In the early stages of the solar system, gas and dust combined to form small bodies known as planetesimals. These objects orbited the young Sun and frequently collided with one another, creating fragments that spread throughout the solar system. Over time, some of these pieces became part of planets and moons, while others survived as asteroids and meteorites.
Meteorites provide scientists with valuable information about the period before Earth existed. The research focused on two types of meteorites: iron meteorites and chondrites.
Iron meteorites are dense metallic objects made mainly of iron-nickel alloy. Chondrites, by contrast, are stony meteorites and account for most meteorites found on Earth today.
Researchers explained that these two groups originated from different generations of planetesimals. Iron meteorites came from the oldest generation of planetesimals, while chondrites formed from a second generation that appeared around two to three million years later.
Using laboratory experiments and geochemical models, the research team created a map of phosphorus-to-nitrogen ratios across the early solar system. Their analysis revealed significant differences between the first and second generations of planetesimals.
The results showed that the first generation had higher phosphorus-to-nitrogen ratios in the outer solar system, with the ratio decreasing closer to the Sun. In the second generation, the pattern was reversed, with higher ratios found in the inner solar system.
Researchers believe that during the formation of the first generation of planetesimals, material flowed outward, increasing the phosphorus-to-nitrogen ratio in the outer regions of the solar system. The situation changed as Jupiter formed and grew.
The study found that Jupiter's increasing size and gravitational influence limited the movement of phosphorus and nitrogen from the inner solar system to the outer regions. As a result, when the second generation of planetesimals formed, those in the inner solar system retained higher phosphorus-to-nitrogen ratios than those farther away.
Senior author Rajdeep Dasgupta of Rice University in Houston said that, for our own solar system, Jupiter's presence and growth history seem to have played a critical role in determining the distribution of the basic chemical ingredients necessary for habitable worlds. He added that it remains an open question whether a life-essential element budget similar to Earth's can be established without a Jupiter-like planet.
Further geochemical accretion modelling showed that Earth's present-day phosphorus-to-nitrogen signature is most closely matched by planetesimals from the inner solar system, whether they were related to iron meteorites or chondrites.
Study lead author Debjeet Pathak, a graduate student at Rice University, said that the research suggests Earth acquired its inventory of the life-essential elements phosphorus and nitrogen primarily from the inner solar system, without requiring a significant contribution from outer solar system chondrites.
