New Study Asks: If Earth Were an Exoplanet, Could Aliens Tell It Has Life?

What would Earth look like to aliens? If they were looking for signs of habitability, what would their observations tell them? It's a lot of fun.

The experiment is more than just fun. It's easier to study our planet and how it looks and then use that information to make better decisions.

According to a new study, finding evidence of life on Earth may be dependent on the season aliens are observing.

There is a lot of excitement when you find a potentially habitable planet. The headlines spread like a bug on the internet.

We've only got a small amount of exoplanets that may be able to support life. There's a long way to go.

We need a lot of science and innovative reasoning before we can say yes. The distant planet is warm.

There is a new study looking at Earth's appearance through different seasons.

The study is called Earth as an exoplanet. The time-variable thermal emission and seasonality of bio-indicators. The author is Jean-Noel Mettler. Mettler is a PhD student in the department of physics at the university.

The history of this type of research goes back to the 70s, when the solar system was visited by spaceships. Pioneer 10 and 11 flew past some of Earth's siblings.

It was the beginning of more detailed analysis of other planets. Scientists learned a lot by measuring the UV and IR.

Today, we are in the time of exoplanets. The same type of observations are being extended to other planets.

The variety of planets we've discovered are interesting, but if there is a Holy Grail in exoplanet science, it is habitability. We want to know if other people live there.

Astronomers are using more powerful instruments to look at distant planets. The same thing would likely happen in another civilization.

The study looked at the effect of different observation geometries on the Earth's emission spectrum.

The researchers looked at how the seasons affect the spectrum. The strength of bio-indicators, such as N 2 O, CH 4 and O 3, depends on both season and viewing geometry.

The study looked at four different observing geometries, one of which was centered on the North and South poles.

NASA's Aqua satellite was used to observe the spectrum with the AtmosphericInfraredSounder.

There isn't a single sample of Earth's thermal emissions spectrum. It is not possible due to the seasonal changes.

The paper states that the strength of biosignature features depends on both season and viewing geometry.

The researchers observed geometry and found that thermal emissions varied a lot. Over the course of time, the variability in readings was greater than above the ocean. The African and North Pole views were centered on land mass.

The northern hemisphere pole-on view has an annual variabilities of 33 percent and the Africa-centered equatorial view has an annual variabilities of 22 percent.

Less variability could be achieved by the thermal stability of the oceans. Smaller annual variabilities can be seen in geometries with a high sea fraction, such as the southern hemisphere pole-on and the Pacific-centered, equatorial view.

This research shows that a living, dynamic planet like Earth cannot be characterized by a single thermal emissions spectrum. This study didn't look into clouds or their effect because there's too much going on.

The authors say future work is required to investigate how cloud fraction, cloud seasonality, and their thermodynamical phase properties affect the detection and result of atmospheric seasonality.

Some variations will be hard to untangle when looking at distant planets. Data that is dirty could make it hard to see them.

The strength of features in the disk-integrated data is usually 10 percent smaller than for Earth. It will be a challenge to untangle the variations from the noise.

Earth is a difficult target for this type of observation due to its complexity.

They explain that remote characterization of planetary environments is very challenging.

We learned that a planet and its characteristics can't be described by a single thermal emission spectrum, but multi-epoch measurement is required.

Most of our discoveries are based on transits of planets in front of their stars. That doesn't have its full capabilities.

We're approaching the day when we'll need to understand better what we're seeing because the James Webb Space Telescope wants to study the spectrum of some exoplanets with more power.

The method of observing exoplanets in mid-Infrared was used in the study. Even though there's seasonal variation and observing geometry variation, our result is not affected by seasonal effects.

According to Mettler and his co- researchers, their method can contribute data to exoplanet observations.

It was concluded that observing exoplanets with thermal emission could provide unique and complimentary information that is necessary for the characterization of terrestrial planets around other stars.

This article was published in the past. The original article is worth a read.