Using Planetary Carbon Cycles as a New Metric for Identifying Intelligent Alien Life

• A new astrobiology framework proposes using Net Primary Production (NPP) as a metric for assessing the evolutionary maturity of exoplanets.
• NPP measures the total carbon converted into organic matter by photosynthetic organisms, providing a proxy for cumulative biological activity.
• This approach moves beyond simply using a star's age to predict the likelihood of intelligent life.

Research Framework

• Based on the Evolutionary Speed Hypothesis (ESH), more biological activity correlates with higher mutation rates and faster diversification, increasing the chances for complex life.
• Benchmarks established from Earth's history:
  • Pre-Cambrian: ~2.4x10^25 grams of carbon fixed (single-celled dominance).
  • Advent of intelligence: ~9.4x10^25 grams of carbon fixed.

Candidate Analysis

• TRAPPIST-1e: Identified as a poor candidate due to tidal locking, dependence on infrared light, and limited precipitation, which restrict photosynthetic potential.
• K2-3d: Identified as a high-potential candidate, with an NPP 1.74 times that of Earth.
• GJ 1061c: Ranked highly with an NPP 1.03 times that of Earth, benefiting from its age (7 billion years) and stellar energy input.

Methodology Limitations

• The model assumes a gradual, incremental evolutionary progression, which may not account for sudden biological leaps like the Cambrian explosion.
• Uncertainties remain regarding the necessity of a "sleep cycle" for biochemical repair on tidally locked planets, potentially invalidating or complicating the NPP assumptions.