and December 25 respectively. The landers carried colour cameras and a soil drill and analyzer, which unfortunately malfunctioned. Each lander made measurements with a nephelometer, mass spectrometer, gas chromatograph, and a cloud-droplet chemical analyzer using X-ray fluorescence that unexpectedly discovered a large proportion of chlorine in the clouds, in addition to sulfur. Strong lightning activity was also detected. In 1982, the Soviet Venera 13 sent the first colour image of Venus's surface and analysed the X-ray fluorescence of an excavated soil sample. The probe operated for a record 127 minutes on the planet's hostile surface. Also in 1982, the Venera 14 lander detected possible seismic activity in the planet's crust. In December 1984, during the apparition of Halley's Comet, the Soviet Union launched the two Vega probes to Venus. Vega 1 and Vega 2 encountered Venus in June 1985, each deploying a lander and an instrumented helium balloon. The balloon-borne aerostat probes floated at about 53 km altitude for 46 and 60 hours respectively, traveling about 1/3 of the way around the planet and allowing scientists to study the dynamics of the most active part of Venus's atmosphere. These measured wind speed, temperature, pressure and cloud density. More turbulence and convection activity than expected was discovered, including occasional plunges of 1 to 3 km in downdrafts. The landing vehicles carried experiments focusing on cloud aerosol composition and structure. Each carried an ultraviolet absorption spectrometer, aerosol particle-size analyzers, and devices for collecting aerosol material and analyzing it with a mass spectrometer, a gas chromatograph, and an X-ray fluorescence spectrometer. The upper two layers of the clouds were found to be sulfuric acid droplets, but the lower layer is probably composed of phosphoric acid solution. The crust of Venus was analyzed with the soil drill experiment and a gamma ray spectrometer. As the landers carried no cameras on board, no images were returned from the surface. They would be the last probes to land on Venus for decades. The Vega spacecraft continued to rendezvous with Halley's Comet nine months later, bringing an additional 14 instruments and cameras for that mission. The multiaimed Soviet Vesta mission, developed in cooperation with European countries for realisation in 1991–1994 but canceled due to the Soviet Union disbanding, included the delivery of balloons and a small lander to Venus, according to the first plan. Orbiters Venera 15 and 16 In October 1983, Venera 15 and Venera 16