India's space agency Isro says it is trying to contact its Moon lander and rover as a new lunar day begins but has not received any signals so far.

The lander, carrying the rover in its belly, touched down near the Moon's little-explored south pole in August. They spent two weeks gathering data and images, after which they were put into 'sleep mode' at lunar nightfall.

Isro hoped the batteries would recharge and the modules would reawaken when the Sun rose around 22 September. But it is possible that the extreme cold of the lunar night damaged the batteries.

Isro recently posted on X (formerly Twitter) that "efforts to establish communication with the Vikram lander and Pragyaan rover will continue". India made history with its Chandrayaan-3 mission when it became the first country to successfully land a spacecraft near the lunar south pole.

It also joined an elite club of countries to achieve a soft landing on the Moon, after the US, the former Soviet Union and China. The landing was carefully planned to coincide with the start of a lunar day, so that Vikram and Pragyaan would have two weeks of sunlight to work with. One day on the Moon equals a little over four weeks on Earth, with the day and night each lasting about 14 days.

The space agency has provided regular updates on their movements and findings and shared images taken by them. While putting them to sleep, Isro said both had completed all their assignments, but expressed the hope that they would reawaken at the start of the next lunar day.

Experts cited the example of China's Chang'e4 lander and Yutu2 rover which did wake up several times with the sunrise. But former Isro chief AS Kiran Kumar said that it was not a given, since night temperatures near the lunar south pole routinely plunge to -200C to -250C (-328F to -418F) and the batteries are not designed to operate or be stored at such extreme temperatures.

Isro has tried to temper expectations, saying if Vikram and Pragyaan do not wake up they will stay on the Moon "as India's lunar ambassador".