Ultrahot Jupiter
These simulated views of the ultrahot Jupiter WASP-121b show what the planet might look like to the human eye from five different vantage points, illuminated to different degrees by its parent star. The images were created using a computer simulation being used to help scientists understand the atmospheres of these ultra-hot planetsNASA/JPL-Caltech/Vivien Parmentier/Aix-Marseille University (AMU)

Planets that are too close to their stars are tidally locked, meaning one side is always facing the star, such planets have weather extremes that are hard to imagine. The permanent day side of these planets are known to have excessive heat and with no chance of rain, these planets are called ultrahot Jupiters.

Almost everything about these planets is extreme, notes a report by NASA. However, one of the more puzzling aspects of these planets is that there is no trace of water vapour anywhere in their atmospheres. More so when water vapour is abundant in slightly cooler planets. Observations made by NASA's Spitzer and Hubble space telescopes of ultrahot Jupiters, mixed in with computer simulations, serve as a starting point for new, theoretical studies that NASA says might have solved this mystery of the missing water vapour.

According to a new study, reports NASA, ultrahot Jupiters have all the right ingredients for the existence of water—hydrogen and oxygen—but because of the intense radiation that these planets' daysides are constantly bombarded with, the heat gets so high that water molecules cannot stay together and are completely ripped to shreds.

Vivien Parmentier, an astrophysicist at Aix Marseille University in France and lead author of the new study, explains that the daysides of these worlds are furnaces that look more like a stellar atmosphere than a planetary atmosphere,  and "in this way, ultrahot Jupiters stretch out what we think planets should look like."

Instruments like Spitzer and Hubble can gather certain things about ultrahot Jupiters and their daysides, notes the report. The nightsides, on the other hand, are not easy to study using current instruments at hand.

The new study has now proposed a model for what researchers think might possibly be happening on both the day and night sides of these planets. This is based largely on observations and analysis of WASP-121b --  an ultrahot Jupiter.

Findings of the research suggests that force from the planets' bright side might actually blow the ripped apart water molecules into the dark side. Once it reaches the relatively cooler side of the planet, hydrogen and oxygen atoms can recombine into water and condense into clouds, drifting back into the hot side to be shredded all over again.

Dayside temperatures on these planets, which are closer to their host stars than Mercury is to the Sun, are estimated to be between 2,000 and 3,000 degrees Celsius. Nightside temperatures, on the other hand, are around 1,000 degrees Celsius cooler. It is cold enough for water to re-form, say the scientists, and, along with other materials like titanium, coalesce into clouds.