India’s space agency has lost touch with its lunar lander as it approached the moon’s south pole.
It’s not clear whether the Vikrum lander has crashed or landed.
The agency said the spacecraft’s descent was normal until 2km (1.2miles) from the moon’s surface. It was supposed to deploy a rover to search for signs of water.
Indian Prime Minister Narendra Modi urged people to hope for the best, during a visit to mission control in the southern city of Bengaluru.
The space agency is analysing data to determine what happened.
Kailasavadivoo Sivan, chairman of the Indian Space Research Organisation, said: Communications from lander to ground station was lost.
The data is being analysed.
Mr Modi added: In life there are ups and downs. And when I saw that the communications was lost, I saw all your faces became… (sad).
This is not a small achievement that you all have done. The country is proud of you. And your hard work has taught us a lot. And like the scientists told me, if we manage to get communications back, it will give us a lot (of information).
Had India successfully landed the craft it would be just the fourth nation to land a vessel on the moon’s surface, and only the third to operate a robotic rover there.
The Chandrayaan-2 mission, which has cost roughly $140m (£114m), was intended to study the permanently shadowed moon craters, thought to contain water deposits, confirmed by the Chandrayaan-1 mission 11 years ago.
Mr Modi’s visit had been to witness the planned landing and congratulate the scientists involved.
Mr Sivan had earlier called the mission the most complex it had ever undertaken.
It lifted off on 22 July from the Satish Dhawan space centre, in Sriharikota, an island off the coast of the southern state of Andhra Pradesh.
Chandrayaan-2 then spent several weeks making its way to the moon, ultimately entering orbit on 20 August.
On 2 September, Vikrum separated from the orbiter and the lander began a series of braking manoeuvres to lower its orbit and ready itself for landing.
The United States, the former Soviet Union and China are the only nations to have landed spacecraft on the moon.
Last January, China achieved the first landing on the far side of the moon. In April, an Israeli spacecraft attempting to land crashed moments before touchdown.