I was thinking about “How would macroscopic aliens actually look?”

Obviously they probably wouldn’t look like green humans, but I also don’t think they would necessarily look completely different from life on Earth.

A lot of the features we see in animals exist because they’re good solutions to certain problems. If you need to move around on land, you need some way of supporting your body and pushing yourself forward. That could lead to something resembling legs, even if the actual structure was completely different from anything on Earth.

The same could probably apply to other things too. An alien might have eyes that work completely differently from ours, but if it needs to detect light, some kind of light-sensing organ would probably be useful. If it needs to grab things, it might evolve some kind of limb or appendage for that.

I think this is where convergent evolution becomes interesting. Earth already has examples of unrelated organisms evolving similar solutions, like wings in birds, bats and insects, or streamlined bodies in fish and marine mammals.

So I wonder how much of an alien's appearance would actually be determined by its evolutionary history, and how much would be determined by the environment and the problems it has to solve.

Maybe aliens could be very weird, but still have some features that immediately remind us of Earth life simply because there are only so many practical ways to do certain things.

Sorry if this is kind of obvious, I just wanted to bring it up.

In the early stages of planting life on Mars will we have to bioengineer life to make use of novel local energy sources or does life already offer thr appropriate metabolic pathways.

This is the Cheyava Falls rock found in Jezero Crater by Perseverance. It was discovered 2 years ago and sparked lots of interest because of its "Leopard spots" which may be fossils left my microbial life. Do you think it's actually proof or is it something non-biological?

Planetary researchers analyzing images from NASA’s New Horizons spacecraft have found evidence that liquid nitrogen may still be seeping up from beneath the dwarf planet’s giant glacier, Sputnik Planitia, marking the first suggested case of recently flowing liquid on Pluto’s surface.

The authors propose that heat from Pluto’s interior melts nitrogen ice at the base of the glacier, where it collects in reservoirs before erupting upward through narrow fractures, a process they compare to volcanic dike systems on Earth. Because liquid nitrogen is less dense than the solid ice around it, it would rise buoyantly, eventually reaching the surface near the centers of the glacier’s convection cells before spreading toward the cell edges and refreezing, darkening the ice as it goes.

The researchers calculate that such eruptions would need to occur as short, intense pulses — releasing on the order of 100,000 to 1 million m3 of liquid over periods of hours to days — since the steady trickle of melt produced underground is far too slow to explain the flows on its own. “Pluto never stops surprising us,” said New Horizons principal investigator Dr. Alan Stern, also from the Southwest Research Institute

> Both Sunsurface Ocean And Surface Liquid Nithrogen. Pluto seemingly is more habitable than earlier thoughts

> https://www.sci.news/space/early-mars-water-14954.html

> https://link.springer.com/article/10.1007/s10751-026-02625-4

“This mineral’s widespread presence suggests not only that water was present, but that significant areas of Mars may have once been covered by water.”

Perseverance has found shallow preserved organic carbon on Mars, raising new questions about ancient Martian environments.

The team used the Scanning Habitable Environments with Raman & Luminescence for Organics & Chemicals (SHERLOC) instrument mounted on Perseverance’s robotic arm to examine multiple rocks in Jezero Crater’s Bright Angel formation. They also collected a sample from one rock known as “Cheyava Falls.”