Can a Muslim woman perform Umrah without a Mahram — or is it required according

[shahrukhkhan]

There is a difference of opinion among scholars about whether a woman must travel with a Mahram for Umrah. Some traditional scholars say it is not permissible without a Mahram because of the hadith that prohibits women from travelling alone, while others allow it if she travels in safety or with a trustworthy group of women.

What do you think the Qur'an and Sunnah truly mean in this case; and why?