Venus is the closest planet to Earth and nearly similar in size and composition. Flight times are short, usually between three and eighteen months depending on the type of mission being flown, and yet it is one of the most neglected planets. The reason may be that Venus has one of the most fearsome environments in the Solar System. Attempt no landing there, but scientists have indeed tried landing spacecraft and succeeded, lasting only for a few hours at best. New missions to Venus are being planned, most of them from the comfort of Venus’s orbit, and India may lead the way.

The Indian Space Research Organization (ISRO) has sent three missions to the Moon in its Chandayaan series since 2008 and one mission to Mars, the Mars Orbiter Mission, affectionately known as MOM, in 2014. It is only logical that Venus is their next target. Venus resides in the inner Solar System with Mercury, Earth, and Mars also known collectively as the terrestrial planets. Mars continues to undergo extensive exploration, and Mercury is also undergoing exploration later this year, but Venus has no missions currently active or enroute. While Venus and Earth occupy nearly the same region near the Sun, there are significant difference between them. Venus orbits the Sun at an average distance of 67 million miles while Earth averages 93 million miles. Venus is expected to be hotter, but the differences between it and Earth are made extreme by their atmospheres. Venus has a thick carbon dioxide dominated (96.5%) atmosphere with an atmospheric pressure 92 times Earth’s. This creates an intense greenhouse effect with an average surface temperature of 870ºF capable of melting lead, tin, and zinc! There is no escaping the heat anywhere on the surface with the highest mountain peaks barely below 700ºF, and worse conditions in the deep canyons and basins, exceeding 900ºF! Night is no cooler than day and the poles are no cooler. Add in some sulfuric acid mist and Venus becomes a planet that cannot be defeated when trying to explore its surface for very long. Venus is better explored with orbiters, or in the cooler atmosphere with balloons and drones, or impactors that could quickly analyze the surface.

Venus remains an enigma despite over 40 visits from spacecraft either flying by, orbiting, or landing. The early missions in the 1960s and 1970s by NASA and the Soviet Union revealed the blistering hot surface conditions and dense atmosphere. These missions provided initial insight into the Venusian atmospheric composition, surface features, and magnetic environment. The few precious surface images from the Soviet Venera landers revealed a desolate flat desert, some littered with rocks split in the searing heat, or distant hills and evidence of hardened lava flows. Later surface images confirmed that the scenery is bathed in an eerie orange sunlight from the thick, hot, dense atmosphere. Later missions expanded the knowledge of the atmosphere including the composition, circulation, and the interaction with the Sun, along with the geography and its geological history. More recent missions, such as Venus Express and Akatsuki, focused on the atmospheric dynamics, climate evolution, and surface features. These missions have provided valuable information on the planet’s unique characteristics and its potential for life in the past. Most of these missions have had either limited global coverage at high resolution or complete global coverage at lower resolution.

The Venus Orbiter Mission (VOM) will provide uniform coverage of Venus and will explore the planet’s atmosphere, surface, and its interaction with the Sun. Key scientific objectives include examining dust in the Venusian atmosphere, mapping surface topography in high resolution, studying the solar x-ray spectrum near Venus, analyzing Venusian airglow, and investigating subsurface characteristics. There are 19 payloads recommended for this mission which includes the Synthetic Aperture Radar for Venus (VSAR) which will search for recent and active volcanism and detect volcanic hotspots, characterize impact craters, ejecta, its impact melt, and globally map Venus at a higher resolution than Magellan. It will measure surface roughness and topography. The Venus Surface Emissivity and Atmospheric Mapper (VSEAM) will also identify volcanic hotspots and study the cloud circulation. The Venus Thermal Camera (VTC) will study the thermal dynamics of the clouds. The Venus Cloud Monitoring Camera (VCMC) will study the atmospheric circulation dynamics, especially near the poles and look for lightning in visible wavelengths. The Lightning Instrument for Venus (LIVE) will measure the field emissions due to plasma and lightning, and listen for whistlers, a sign of lightning, its strength, frequency, and duration.

There are several other instruments that will study Venus at a resolution not yet achieved. One of the more interesting ones will produce a global map of the surface temperature that will finally reveal how temperature varies with altitude and topography across the entire planet. Venus Express had an instrument that could do this but failed to deploy and only isolated locations were mapped using another instrument at a lower resolution. Scientists will finally have a refined temperature profile of the surface that will be crucial to determine the climate across the plains, lowlands, canyons, and mountains. The frost line for the exotic metallic frost deposits of lead and bismuth can be mapped on the cooler high peaks. How the atmosphere flows among the mountains will be followed as ripples form and dissipate in the clouds high above them, already observed by Venus Express. Changes in the surface from suspected volcanic eruptions can be monitored during the planned 5-year life of the mission. Studying the atmosphere of Venus is different than Earth in that it is so thick, it is more like studying an ocean. Winds behave like a fiery current beneath the clouds and being laced with sulfuric acid in such a dense atmosphere with ferocious heat could create interesting chemistry and effects on its environment.

Launch of the Venus Orbiter Mission is scheduled for March 29, 2028, with arrival hardly four months later, July 19. It will go into a highly elliptical orbit at first, 300 x 37,000 miles, and then use aerobraking, skimming through the upper atmosphere for six to eight months, to bring it to its operating orbit of 120 x 360 miles in a near-polar orbit. The polar orbit will assure global coverage of Venus in high resolution of the surface, atmospheric/cloud dynamics, and the ionosphere.

The Venus Orbiter Mission may pave the way in the next era of the exploration of Venus, if it launches on time and succeeds. It will be followed by NASA’s VERITAS orbiter and the DAVINCI atmospheric probe, and ESA’s Envision orbiter during the early 2030s. When all the data is in hand and thoroughly studied, another wave of exploration will see landers, rovers, and possibly a sample return mission. There is so much still to learn and understand about Venus. Nothing will defeat the human spirit to explore.