On 11 April 2006, the first European spacecraft arrived at Venus to stay. Approved only three years before its launch, late 2005, Venus Express is the fastest mission ever managed by the European Space Agency to date. I recall serving on the Solar System Working Group in 2002. This is one of the four advisory bodies for ESA’s Science Programme with rotating members from the relevant science communities. We were presented with a mission opportunity to use spare elements from the Rosetta mission (launched in 2004) and the Mars Express mission (launched in mid-2003). Rosetta was a cornerstone mission in ESA’s Science Programme, developed from scratch. Mars Express was a spin-off of Rosetta, and hence Venus Express can be considered a grandchild of Rosetta. Of these three missions, Mars Express is still orbiting Mars and collecting useful scientific data. The fast development track for Venus Express was, of course, thanks to the reuse of the existing spare spacecraft bus and spare instruments.

The decision by the ESA member states to use the Rosetta and Mars Express spares to go to Venus was taken in 2002, the contract with industry was formally signed in early 2003 (Fabrega et al. 2003), and the launch occurred in late 2005. The mission formally ended in December 2014, and the spacecraft was sent into the atmosphere of Venus to disintegrate.

The mission cost on the industry side was under 100 Meuros, less than 10% of the cost of the Rosetta mission, and I think it is fair to state that the science-per-Euro-ratio for Venus Express must be one of the best of all missions of the agency to date.

ESA’s task is to take care of providing the spacecraft, through European industry, getting it to its destination, and operating it. The payload, however, the instruments, are made by dedicated teams of scientists and engineers from European institutes, and are paid for separately by ESA member states. Just one of the seven instruments on Venus Express, the Venus Monitoring Camera, was newly developed. The other six were inherited from Mars Express (ASPERA, PFS, and SPICAV) and Rosetta (VIRTIS, VeRa, and MAG).

Venus Express marked a return to Venus! The last dedicated mission to Venus had been Magellan (NASA), which mapped the surface of Venus for the first time using radar, and studied the gravity field, between late 1990 and late 1994. It carried no other instruments.

Between Magellan and Venus Express, two spacecraft used Venus’ gravity to gain speed on their way elsewhere: Galileo to Jupiter in February 1990, Cassini/Huygens to Saturn in April 1998 and June 1999. On these occasions, useful data, but limited amounts, were collected. In fact, the Galileo Near Infrared Mapping Spectrometer data provided with the confirmation of theoretical calculations presented a few years earlier, that pointed at the existence in the near infrared of a narrow window, at 1.18 micron, through which the surface can be observed, albeit not very ‘sharp’ due to atmospheric interference: like seeing the bottom of a lake through a column of moving water (Kamp et al. 1988, Carlson et al. 1993). Ever since Galileo confirmed this possibility, any spacecraft going to Venus has been carrying the capability to observe this wavelength range.

The VIRTIS instrument and the VMC camera on Venus Express both covered this wavelength region. One of the results that caused excitement was the observation that surface emissivity values derived from VIRTIS data in regions related to volcanic structures are very high compared to the rest of the surface. This could be indicative of recent volcanic activity (Smrekar et al. 2010). More recently, reanalysis of Magellan radar data showed changes at the surface in a two-year time span, which could be related to current lava flows (Sulcanese et al. 2024) and the existence of lava tubes (Carrer et al. 2026).

Venus Express collected data about the sulphur dioxide (SO2) concentrations at the cloud levels during its active years. Before Venus Express, data collected by the Pioneer Venus mission (NASA) between 1978 and 1992 revealed that the abundance of SO2 decreased significantly over that time period. The mystery of the variation of SO2 at the cloud levels deepened as data from Venus Express added to the long timeline: it showed a steep rise at the beginning of the mission, followed by a similar decline as seen with Pioneer Venus over several years (Marcq et al. 2012). Whether or not this is connected to episodes of volcanic activity remains unclear at this point, but the possibility exists. Long-run ground-based observations (2012 – now) performed and presented by Encrenaz et al. (2025 and references therein) point to the existence of strong variation at short and long temporal and spatial scales from regional to global.

After Venus Express, the Japanese Akatsuki mission collected a large data set between 2015 and 2024, when contact was lost. Today, there is no spacecraft orbiting Venus. A new mission is being developed at this moment at ESA called Envision. It will become active in the mid 2030s. With a powerful suite of instruments, Envision will be observing Venus from the interior all the way to the upper atmosphere. The collected data will also be used to address the SO2-mystery, and more discoveries are to be expected! In the meantime, we have to continue to observe Venus from Earth and from the rich space-based data sets that exist and that most certainly contain several hidden treasures to be uncovered.

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