The closest Earth-like planet to Earth is Venus. It's located in our own solar system and shares many similarities with Earth, such as a comparable size and mass. However, its atmosphere is much denser and consists mostly of carbon dioxide, making it an inhospitable environment for life as we know it.
The closest known Earth-like exoplanet, Kepler-438b, is located in the habitable zone of its star, which is around 470 light-years away from our solar system. It's approximately 12% larger than Earth, and astronomers believe it could have liquid water on its surface. However, more research is needed to determine if it's truly Earth-like and if it has a habitable atmosphere.
Astronomers believe that Kepler-438b might have liquid water on its surface due to several factors. First, its size suggests that it could have a solid surface and not be a gas giant like some other exoplanets. Second, its orbit within the habitable zone of its star means that the planet's surface temperature could be within a range where water could exist in a liquid state. Third, the star it orbits, Kepler-438, is slightly cooler and smaller than the Sun, which may result in a more stable climate on the exoplanet. However, these are just indications, and direct confirmation of liquid water or the presence of life requires further study and observation.