M4 – ARIEL

The European Space Agency's M4 mission, ARIEL (Atmospheric Remote-sensing Infrared Exoplanet Large-survey), is a mission designed to study the atmospheres of exoplanets using infrared spectroscopy. This mission was selected in 2018 as the fourth medium-class mission in ESA's Cosmic Vision programme and is expected to launch in 2029. In this article, we will discuss the when, why, how, cost, and expected achievements of the ARIEL mission.

When is the ARIEL mission launching?

The ARIEL mission is currently scheduled to launch in 2029. The exact launch date is not yet confirmed, but the spacecraft is expected to be launched from Kourou in French Guiana on an Ariane 6 rocket.

Why was the ARIEL mission proposed?

The ARIEL mission was proposed to study the atmospheres of exoplanets using infrared spectroscopy. The study of exoplanet atmospheres is essential in understanding the formation and evolution of planetary systems and in the search for habitable worlds beyond our solar system.

ARIEL's primary scientific goal is to observe and characterize the atmospheres of around 1,000 exoplanets orbiting a wide variety of star types. By studying the chemical composition, thermal structure, and vertical mixing of exoplanet atmospheres, ARIEL will provide a comprehensive understanding of the physical and chemical processes that shape exoplanets.

How will the ARIEL mission work?

The ARIEL mission will use a 1.1-meter diameter telescope to observe exoplanets as they pass in front of their host star. During these transits, ARIEL will use its infrared spectrograph to analyze the light passing through the exoplanet's atmosphere. By studying how the atmosphere absorbs and scatters light at different wavelengths, ARIEL can determine the composition, temperature, and pressure of the atmosphere.

ARIEL will focus on observing exoplanets that orbit close to their host stars, known as hot Jupiters, super-Earths, and sub-Neptunes. These exoplanets are easier to observe because they block a significant amount of their host star's light during a transit. ARIEL's observations will be complemented by ground-based observations from the James Clerk Maxwell Telescope and the Atacama Large Millimeter/submillimeter Array.

The ARIEL spacecraft will be placed in a halo orbit around the second Lagrange point of the Earth-Sun system, approximately 1.5 million kilometers from Earth. This orbit will allow ARIEL to have an unobstructed view of the sky and a stable thermal environment, which is crucial for making precise infrared measurements.

What is the cost of the ARIEL mission?

The total cost of the ARIEL mission is approximately €450 million ($495 million). This cost includes the development, launch, and operations of the spacecraft, as well as the scientific payload and ground segment.

The ARIEL mission is a collaboration between ESA and several European countries, including the United Kingdom, France, Italy, Poland, Spain, Belgium, Austria, Denmark, Ireland, Hungary, and Portugal. In addition, NASA has provided scientific and technical support to the mission.

What are the expected achievements of the ARIEL mission?

The ARIEL mission is expected to make significant contributions to our understanding of exoplanet atmospheres and the formation and evolution of planetary systems. Specifically, ARIEL will:

* Provide the first comprehensive survey of the chemical composition and thermal structure of a large sample of exoplanet atmospheres.

* Identify the major atmospheric constituents of exoplanets, including water vapor, carbon dioxide, methane, and nitrogen.

* Determine the temperature profiles and vertical mixing of exoplanet atmospheres, providing insights into the atmospheric dynamics and energy transport mechanisms.

* Characterize the properties of exoplanet clouds and hazes, which can affect the transmission and reflection of light in the atmosphere.

* Study the diversity of exoplanet atmospheres, including those of different sizes, masses, and compositions, and the effect of stellar radiation on their evolution.

* Search for biosignatures in the atmospheres of exoplanets, such as oxygen and methane, which could indicate the presence of life.

The data collected by ARIEL will be made publicly available, enabling scientists worldwide to conduct further research on exoplanet atmospheres and planetary systems. ARIEL's observations will also inform future missions, such as the James Webb Space Telescope, which will be able to follow up on ARIEL's findings with higher spatial resolution and sensitivity.

In conclusion, the ARIEL mission represents a significant step forward in our understanding of exoplanet atmospheres and the search for habitable worlds beyond our solar system. With its advanced infrared spectroscopy capabilities and large survey of exoplanets, ARIEL has the potential to revolutionize our understanding of planetary systems and the conditions necessary for life.