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S. Masiero and M. S. Erculiani
stars. Most of them are very different from those of the Solar System and one of the
striking case is that of the super-Earths, rocky planets with masses ranging between
1 and 10 M ⊕ with dimensions up to twice those of Earth. The long list motivates
many scientists to consider which of these worlds could support life and what type
of life could live there. One of the most fascinating questions is probably what color
alien plants would be. The question matters scientifically because the surface color
of a planet can reveal whether anything lives there—specifically, whether organisms
collect energy from the parent star by the process of photosynthesis. Photosynthesis
is adapted to the spectrum of light that reaches organisms. This spectrum is the result
of the parent star’s radiation spectrum, combined with the filtering effects of the
planet’s atmosphere and, for aquatic creatures, of liquid water. Light of any color
from deep violet through the near-infrared could power photosynthesis. Around stars
hotter and bluer than our Sun, plants would tend to absorb blue light and could look
green to yellow to red. Around cooler stars such as red dwarfs, planets receive less
visible light, so plants might try to absorb as much of it as possible, making them
look black. The ExoBioLaboratory aims to promote the student’s curiosity about
this area of research, and to make it more attractive through hands-on learning. As
students now become protagonists, the motivation therefore appears for them to shed
the passivity and estrangement with which they often react to face-to-face lessons.
The main activity is to recreate a plausible exoplanetary environment—imagining
a Super-Earth orbiting around a star and considering what kind of plants could be
born there, and generally speaking, what types of plant life could evolve on such a
planet. By educating children about the life-essential conditions here on Earth and
comparing them to those of other worlds, they learn that this is the only place in
the universe that is suitable for life as we know it, which promotes respect for the
environment and a sense of a global community.
9.2 Background Information
9.2.1 Ingredients to Sustain Life
The most important ingredient to sustain life as we know it is liquid water. The
presence of liquid water depends on environmental conditions like air temperature
and atmospheric pressure. The main driver of the surface temperatures of planets is
their distance from the central star they orbit. The temperatures are just right only
in a small window so that water does not completely evaporate or freeze. These
conditions are modified by local influences like the density of the atmosphere and
the composition of potential greenhouse gases. This defines a range around a given
star in which liquid water could be present. This range is defined as the “habitable
zone”. If a planet is found orbiting in this zone, it may potentially possess water in the
liquid form and thus sustain life as we know it. In the Solar System, Earth occupies
the habitable zone. There is no guarantee that any planet orbiting within the habitable
zone actually possesses notable amounts of liquid water or harbours life, because the
S. Masiero and M. S. Erculiani
stars. Most of them are very different from those of the Solar System and one of the
striking case is that of the super-Earths, rocky planets with masses ranging between
1 and 10 M ⊕ with dimensions up to twice those of Earth. The long list motivates
many scientists to consider which of these worlds could support life and what type
of life could live there. One of the most fascinating questions is probably what color
alien plants would be. The question matters scientifically because the surface color
of a planet can reveal whether anything lives there—specifically, whether organisms
collect energy from the parent star by the process of photosynthesis. Photosynthesis
is adapted to the spectrum of light that reaches organisms. This spectrum is the result
of the parent star’s radiation spectrum, combined with the filtering effects of the
planet’s atmosphere and, for aquatic creatures, of liquid water. Light of any color
from deep violet through the near-infrared could power photosynthesis. Around stars
hotter and bluer than our Sun, plants would tend to absorb blue light and could look
green to yellow to red. Around cooler stars such as red dwarfs, planets receive less
visible light, so plants might try to absorb as much of it as possible, making them
look black. The ExoBioLaboratory aims to promote the student’s curiosity about
this area of research, and to make it more attractive through hands-on learning. As
students now become protagonists, the motivation therefore appears for them to shed
the passivity and estrangement with which they often react to face-to-face lessons.
The main activity is to recreate a plausible exoplanetary environment—imagining
a Super-Earth orbiting around a star and considering what kind of plants could be
born there, and generally speaking, what types of plant life could evolve on such a
planet. By educating children about the life-essential conditions here on Earth and
comparing them to those of other worlds, they learn that this is the only place in
the universe that is suitable for life as we know it, which promotes respect for the
environment and a sense of a global community.
9.2 Background Information
9.2.1 Ingredients to Sustain Life
The most important ingredient to sustain life as we know it is liquid water. The
presence of liquid water depends on environmental conditions like air temperature
and atmospheric pressure. The main driver of the surface temperatures of planets is
their distance from the central star they orbit. The temperatures are just right only
in a small window so that water does not completely evaporate or freeze. These
conditions are modified by local influences like the density of the atmosphere and
the composition of potential greenhouse gases. This defines a range around a given
star in which liquid water could be present. This range is defined as the “habitable
zone”. If a planet is found orbiting in this zone, it may potentially possess water in the
liquid form and thus sustain life as we know it. In the Solar System, Earth occupies
the habitable zone. There is no guarantee that any planet orbiting within the habitable
zone actually possesses notable amounts of liquid water or harbours life, because the